All right, so welcome everyone. I'm really happy to be back and giving another lecture for the webinar vet series on oncology. And today we're gonna cover, actually, two series of, of, kind of the less common things that we see around the head and neck area, so oral tumours, which again is a lecture that I think many people get, it's something that we're not gonna cover here, but we'll be doing sort of most of the other.
tumours that we see besides the common ones of the oral cavity. And this first hour, is actually gonna be dedicated primarily to nasal tumours. But then we will talk just a bit, at the end about thyroid tumours as well.
And again, as with the previous lectures, this is obviously, not being done in a real-time interactive way but being pre-recorded, for you to download and, and view, at your leisure and as a result, we can't really sort of exchange information about questions and answers. So, please, please, please feel free to utilise that email address that's at the bottom of this slide with any questions that you have either about the content of this lecture or really anything else that has to do with oncology. I'm always happy to answer those questions.
So, without further ado, why don't we get started and we'll start talking about nasal cavity tumours. So, just some background, about nasal cavity tumours. We do see them with some frequency, here at CSU and I think in general, they're, not the most common things that we see, but not tremendously rare.
In general, we do tend to see, just like with most other kinds of cancer, these occur in older animals, and they do seem to be more common in dogs than they are in cats, although we certainly can see them in cats as well. There are some studies that suggest that, dogs who live in an urban environment. Or dogs that are exposed to passive cigarette smoke might be at increased risk of development of these tumours and that sort of implies that some type of air pollution, may be a risk factor for these animals.
The other additional risk factor that's been identified is basically the length of your nose. So, dolichocephalic breeds like the collie that you see at the top there, do tend to have a higher risk of nasal tumours than the brachycephalic breeds like the little pug that you see on the bottom. And the, the sort of simple explanation for this is, is really a statistical one that dogs with longer noses have more nose cells.
So just by pure dumb luck, there's a higher chance that one of those nose cells may be able to transform into a tumour. So, what kinds of tumours do we see up the nose? So in dogs, about 2/3 of the tumours that we see are carcinomas, so generally tumours that are starting either from the lining of the nasal cavity or from some of the glands.
That are in the nasal cavity. About 1/3 of the tumours that we see can be sarcomas, and these can be arising from bone, from cartilage, or occasionally again from just sort of the fibrous connective tissue that holds everything together. Certainly, we can see our share of oddball other kinds of tumours up the nose as well.
We can see transmissible venereal tumour up the nose, the occasional mass cell tumour, the occasional lymphoma, etc. In cats, probably 60%, maybe 70% of all the lymphomas that we're gonna see, I'm sorry, all the nasal tumours that we're gonna see are actually going to be lymphoma. And actually in the majority of cats, these are going to be solitary at presentation.
So rather than being some bizarre manifestation of, multicentric or systemic lymphoma, often it really is just isolated to the nasal cavity at the time of presentation. So, how do we expect these tumours to behave? So, most of the time, we really consider a lot of these to be local problems.
So, they're problems because of the stuff that they do actually up the nose that's obstructive and destructive and resulting in things like sneezing and difficulty breathing and epistaxis, etc. So we certainly can see metastatic disease occur. It generally occurs late in the course of the disease and again with the carcinomas, which is the most common thing that we see in dogs.
We can see lymph node involvement, that's often the first place that we'll see, this go. And then we can see lung involvement, down the line as well. Brain involvement can be observed, but that's more often a result of local extension of the tumour through the cribiform rather than true metastasis.
And then, strangely enough, when cats, with, primary, sorry, primary nasal lymphoma do develop disease outside of the nasal cavity. It's often the kidneys. That are involved.
So, one of the interesting things, at least in the dogs, is that metastasis is actually rarely the cause of death in these patients. So despite the fact that necropsy studies can suggest that upwards of 40% of dogs with nasal tumours may have evidence of metastasis at the time of death, it's almost always local disease that's actually the cause of their decline. So that's really where we focus the vast majority of our attention therapeutically.
So, how's a dog with a nasal tumour going to show up at your practise or cat for that matter? So by far and away the most common clinical presentation is going to be epitaxis. We can see other characters of nasal nasal discharge, so from serous to serro sanguinous, to supparative to purulent, but, epitaxis would be the most common.
Historically, it's quite common for the owners to report that it started out unilateral and then progressed to bilateral epistaxis over time. That's not always the case, however. And again, obviously, it is important to remember that, that epistaxis is not the only, I'm sorry, Epitaxis is not the only clinical presenting complaint that we can see.
And a nasal tumour is also not the only differential diagnosis for a dog that has, an epistaxis episode. So here are some of the other things that we'd want to consider using the, the dammit scheme, that we probably all learned in vet school. So if you look at autoimmune disease, we certainly can see sort of primary inflammatory rhinitis like lymphoplasmatic or eosinophilic rhinitis in my, hands, I think the kinds of discharge, the character of the discharge that we're likely to see in those cases is more likely to be, kind of, purulent or muoid rather than epistaxis, but you certainly can.
Metabolic things like hypertension and coagulopathy can definitely be associated with epistaxis. So those would need to be on our list. Infectious diseases, so nasal foreign bodies, fungal or bacterial rhinitis, tooth root abscesses, those kinds of things are obviously quite possible as well.
And then we can certainly see trauma as well leading to epitaxis. But unfortunately, I think in an older dog without a history of trauma, who has unilateral epistaxis, a tumour would actually have to be fairly high up on our differential list. Some of the other things that we certainly could see, dogs like this present for are things like sneezing, even in the absence of epistaxis or other kinds of nasal discharge, upper respiratory stridor, fac facial deformity, like you can see in these two patients here, exophthalmos, which is usually unilateral.
And again, occasionally dogs can present with CNS signs as well. And again, the reason for that is we certainly can see dogs who have nasal tumours that have penetrated the, the cribiform plate, as is evidenced by this MRI here from a, a bearded collie that presented with seizures, where again, obviously, there's a very, very large nasal component. To this disease, but it actually has extended back through the cranial vault, and into, the olfactory lobe of the brain.
So one of the other things that I do tend to like to mention is that often, an owner who presents, their dog with this kind of, of history may not necessarily be gung ho to do an incredibly thorough workup at the very, very first time, a, a clinical sign of nasal disease is seen. So it's quite common for us to be sort of faced with treating some of these dogs empirically with things like antibiotics or different kinds of anti-inflammatories, whether NSAIDs or steroids. And one of the things that, that we always like to sort of impress upon the owners and the students when we're teaching about this is that some amount of resolution of clinical signs as a result of the use of things like antibiotics or anti-inflammatories does not rule out a tumour as an underlying cause.
So it's quite common for these kinds of diseases, these kinds of tumours to be secondarily infected. And certainly associated with a lot of perit-tumoral or intra-tumoral inflammation. So again, these symptomatic treatments certainly have the potential to, again, decrease some of the inflammation, decrease some of the secondary bacterial colonisation, and again, potentially be associated with some improvement of clinical signs where the underlying disease is still present.
So that's why again, if we do have an owner who chooses initially to treat empirically, we always like to say, hey, this may or may not be the root cause of our problem and if those signs recur, we really will need to be a bit more aggressive or thorough with our diagnostics to figure out what's going on. So, what are some of the things that we wanna pay attention to on our physical examination? Specifically, if we have a dog where we're worried about the possibility of a, of a nasal tumour.
And again, I am saying dog, but this would apply equally to a cat. So we do like to look at air flow. So, is there in fact equal air flow out of both nostrils, or is there one that appears to be plugged?
And this can be done through the slide test that you see in the lower, lower right here, where you actually hold the glass slide in front of the areas and actually look for equal fogging on both sides. But the other thing that you can simply do is occlude one nostril and then the other and see if, again, there's air flow out of both nostrils that way. Is there crusting at the areas and what's the character of that crusting?
Again, does it have a, a character that's consistent with epitaxis? Does it look more muoid or mucopurulent, etc. Facial symmetry is a very, very important one.
So generally, we like to really inspect the dog's face and head for evidence of symmetry. So we look from above, we look from the front, we look from the side. Does it really appear to be symmetrical on both sides?
And again, part of that symmetry actually goes to retropulsion of the eyes. So, do the eyes actually retro Pulse equally? Is there one that seems like it's more resistant to retropulsion than the other?
We also like to do a good oral examination as well. So if we open up the roof of the mouth, is there any evidence of palatal deformation, or again, asymmetry? Is there any really obvious evidence of, of incredibly bad teeth that might increase your risk or your, index of suspicion for something like, a tooth root abscess.
So all of those things would be things to keep an eye on. And then we definitely like to. Carefully palpate the regional lymph nodes as well.
So again, as I mentioned, the majority of these animals will not have metastatic disease at presentation, but if in fact you do feel evidence of enlarged lymph nodes, that's unquestionably something that you want to investigate. So again, the likelihood of seeing a positive lymph node at the time of diagnosis is only about 10%. But one of the thing, the reasons in addition to sort of wanting that information for, for clinical purposes that I think is incredibly useful is if in fact you're able to achieve a diagnosis of a carcinoma, for example, via aspiration of a regional lymph node.
That's an incredibly simple and inexpensive and non-invasive way to actually achieve a diagnosis versus the diagnostics that we'll talk about. If we need to actually interrogate what's going on inside the nasal cavity. So we'll always try and do that if we can feel anything that feels unusual.
Chest X-rays are a great thing to do again. Very, very few dogs are gonna be positive at the time of diagnosis, but again, a really worthwhile insurance policy. Often, either the, the diagnostics that are gonna be required or the therapeutics that are going to be required, will require some amount of anaesthesia.
So your standard pre-anesthetic blood work is very helpful. We will sometimes consider doing coagulation studies on these dogs again, if there's something about this dog that makes us sort of rank coagulopathy, perhaps a little higher on our differential list than for an average dog. And we definitely do like to look at a blood pressure, and again, part of that is again because primary severe hypertension, it can be associated with epistaxis.
And again, it's something that we want to know about as we're sort of going down the road towards our diagnostics. If that's something that needs to be managed to minimise. For example, biopsy associated haemorrhage associated with the procedure.
So some kind of imaging is usually gonna be a really important part of working up these dogs. And one of the quickest and easiest and cheapest kinds of imaging that we can do, and it's something that almost all of us can do in our practise, is a good set of radiographs. And I think most of us are probably familiar if we sort of harken back to our vet school days about sort of these very, very complicated nasal series, quote unquote, that that sort of we can request and that the, the radiologists can do for us that involve, I don't know, 6 or 7 different views.
You know, with obliques and skyline views and all these other kinds of things. But really, honestly, if our, if our interest is in the nasal cavity per se, and a tumour is very high on our differential list, it's probably the open mouth ventro dorsal view that is actually gonna give us the most reliable information and the most useful information. So if we have to cherry pick or, you know, carefully select the views that we get, this is really the one that's going to give us the, the most information.
And one of the things that's really important is that these dogs be positioned extremely accurately in order to actually make this, this view work. So, almost always, this is gonna require general anaesthesia. And again, one of the things that's gonna be incredibly helpful.
Is if we have a a radiograph head that is capable of of going out of the out of the perpendicular plane, so we can actually shoot down at an angle, retract the lower jaw, and that actually allows us an unobstructed view of the nasal cavity as you see in this picture right here. And in general, really the kinds of things that we are primarily looking for in this particular view is symmetry. Again, just like with our physical examination findings.
So the things look the same on one side as on the other side. So in this particular case, you can see, wow, it does look like there's a lot more soft tissue opacity in this right side of the nasal cavity. And again, obviously, this is a very non-specific finding, so there's a million different kinds of things that could be up the nose that would have this appearance.
This could be all fluid, this could be soft tissue, etc. Etc. But obviously, you can see that there's a difference between these two sides and that would certainly increase your index of suspicion.
Some kind of pathology up the nose. But again, some of the other things that you can keep your eyes out for are things like, again, is there evidence of turbinate loss, lysis or deviation of the septum or the other parts of the cortical bone. Can you see evidence of lysis of the soft palate?
You wouldn't appreciate that necessarily on this view so well. And again, with those sinus shots, you could actually potentially see some opacity in the frontal sinus as well. Again, not gonna be able to tell the difference between a buildup of fluid.
Secondary to some downstream obstruction and soft tissue like you'd see with tumour but still something that would be informative as well. But really, ultimately nowadays, we find that we get a lot more information from three dimensional imaging and generally CT scan is our preferred methodology for that versus MR. So MRI is absolutely wonderful as a diagnostic tool, and it gets you beautiful images of, of the head, including the soft tissues, etc.
However, since the treatment of choice for nasal tumours, as, as most of you probably know as radiation therapy, radiation therapy cannot be planned, utilising MR images very effectively. It almost always requires a CT. So really having access to a CT, is gonna sort of facilitate radiation planning if you have an owner who's planning on going that route.
So, when we see a CT scan of a nasal tumour again, the thing that we're primarily interested in is symmetry. So the things look the same on one side as the other. So here's an example of an a normal nasal cavity and as you can see, we're right at the level of the lenses here of the eye.
So in the middle of the nasal nasal cavity, we're just starting to get a little touch of cribiform plate in here in this view. And again, you can see nice air-filled, turbinates, things look the same on both sides versus, again, here's a dog with a nasal tumour where we can see one side is Completely filled up, soft tissue that's sort of heterogeneously contrast enhancing does appear to be crossing over midline just at this little point. And we do have evidence of bony lysis sort of up through the doors, some of the nasal bones and into the soft tissues.
So this dog would have obviously pre presented with evidence of, a mass, or asymmetry that you could see on the outside of the body. And again, on this, different view here, you can actually see again evidence of penetration, up through the frontal sinus, and into the soft tissues on the outside of the head. So, rhinoscopy is another thing that's talked about a lot.
So should we actually stick scopes up the nose to kind of see what's going on up there. So it can be a very, very useful test, especially if we're trying to diagnose and potentially retrieve something like a nasal foreign body. It's an incredibly useful tech technique and actually probably the, the technique of choice for diagnosing nasal mites.
That's always really fun when you can see those little critters running around up there. But, and it comes in two flavours. So actually, you can take a rigid scope and actually go in an anterior grade direction actually through the areas and up into the, up into the nasal cavity that way.
And, again, here's an example of what sort of normal turbinates would look like versus this highly, highly irregular and, and abnormal appearing turbinate structures that you would see in a dog with a tumour. And you can also go behind the soft palate and retroflex to look that way with a . With a, a flexible scope as well, and that can sometimes give us additional information that can be very useful.
So, you certainly can, get, samples that are obtained through these little tiny scopes, that you can submit for histopathology. And again, the theoretical advantage of that, especially if you have a flexible scope of the biopsy port is that you can directly visualise the tissue that you're biopsying and sort of shoot for something that looks abnormal. However, the big downside is that the pieces that you're gonna get through these scopes, they are very, very, very small and often very, very, very superficial often.
So in theory, I think there's a potential risk for an increased negative biopsy result or non-diagnostic biopsy result if we only use this sort of transendoscopic approach. So, another approach that can be used is what's called a nasal flush, and one of the theoretical advantages to this technique is that these are the only things you need, with the exception of a biopsy cassette actually to be able to do this procedure. It's a very, very simple procedure.
So, again, basically what you do is you fill up to the absolute brim. bulb syringe like this one that you use for doing ear flushes and things like this with saline. Doesn't have to be sterile necessarily, but it usually is.
And then, again, sort of cram, the little end of this bulb syringe up into the, the nasal cavity, really as far as you can. And the goal is to make an incredibly tight seal. Across this little area right here and then really vigorously push fluid up into the nose, to actually flush out, potentially debris, foreign bodies and potentially pieces of tumour tissue as well.
So obviously, it's absolutely critical when this procedure is performed that this animal be intubated and that you have a, a fully inflated, ET tube. And the reason for that is, you know, you certainly do not want to be flushing this material down into the poor dog's lungs. So again, it can be diagnostic.
You can sometimes flush out very, very sizable pieces of tissue from the, these cats and dogs' noses that you can submit for histopathology. Again, it's also very comparatively atraumatic. And it can sometimes be therapeutic if you flush out something like this, this, what we call here in the US a grass on, but again, some kind of plant material that a dog has managed to hook up their nose and could be responsible for their clinical signs.
So, get a really interesting and potentially useful technique. That does not require a lot of, of very specific equipment. And again, the other theoretical advantage to this procedure is actually that most of the time after a successful nasal flush, this can also be very palliative.
So despite the fact that, again, it's not going to be a curative technique, these animals generally wake up and they do have reductions in their clinical signs just cause you've cleared out about that, much of that inflammation and, and junk that's up there, even if it is secondary to a tumour. Another procedure that you could consider is what's called a pinch biopsy. And again, it does not require a tonne of very sophisticated equipment.
Really, the only pieces of equipment that this requires are pinch forceps. And these can be bought from really any medical supply house. There are a couple $100 US dollars.
They're fully metallic and as a result, they can be steam sterilised, so they don't require any special sterilisation. And that's really the only piece of equipment that's required for, for a pinch biopsy of the nose. So generally, you can sort of plan your attack or, or exactly where you're gonna get your sample from based on the imaging that you've done, whether that's flat radiographs or whether that's something like a CT scan, and get an idea at least about, hey, does this look like something where I wanna be, you know, towards the front of the nasal cavity, towards the back of the nasal cavity.
Again, with three-dimensional imaging like CT you might even be able to say I wanna be a little bit more dorsal. I wanna be a little bit more ventral, etc. But when you actually do that procedure, this is what it looks like.
One of the very, very most important things that we absolutely, positively try to hammer home with our students is, it is incredibly important not to advance this PINS biopsy instrument too far into the nose, or you could end up sampling the brain. And, I hate to say it, but that is something that has happened at CSU thankfully, it was before my time, but, but it can occur. So we always want to make absolutely sure that we measure carefully to know how far we can advance our biopsy instrument without risking an accidental brain biopsy.
So how do we do that? It's actually very, very simple. So if we measure from the tip of the nas to the medial canthus of the eye on the side that we're going to introduce the biopsy instruments, there is no way you can hit the brain.
And this actually goes for a dog with any shaped nose. So it's actually a very reliable, methodology for avoidance of hitting the brain. And then it's nice to put a little piece of tape or something right at that spot, so you know, oh my, I better not go in any further than this, or some really bad stuff could happen.
So, utilising this kind of biopsy procedure, one of the things that we certainly do know is we can see some post biopsy haemorrhage. And this is something that we are always prepared for. We always tell the owner to expect it.
It is rarely severe, it's rarely life-threatening. But again, there's enough potential for this sort of post biopsy, increased epistaxis. That we do generally offer, to keep a dog overnight.
Obviously, if, if they're in a 24 hour facility where there's somebody that's there watching them. Again, not necessarily so much because we're really terribly afraid of, of life-threatening haemorrhage, but more because we'd like to give the the owner the option to avoid having the dog sneeze blood all over their house. Sneeze blood all over their car on the way home, those kinds of things.
We certainly can see the occasional dog who could run into a more severe epistaxis situation postoperatively. And then again, there are some sort of tips and tricks that we use. Our anaesthesia folks actually like very much to put a mixture of lidocaine and epinephrine up the nose before the biopsy procedure, which just helps to sort of contract or constrict those blood vessels that are up there.
Sometimes during recovery. If we have an animal, especially who's a bit anxious or might be sort of struggling a little bit, something like aromazine can actually be very useful because obviously it has some sedative properties, but it also lowers their blood pressure. So those kinds of things can sometimes be quite helpful.
Again, just to mitigate. Non-severe, sort of post biopsy haemorrhage. Again, once in a once in a great while, maybe once in a couple 100 cases, we could see more severe haemorrhage, but actually that's quite rare.
So we can see quite a bit acutely, but again, it usually stops on its own relatively quickly. Another procedure that we could consider is what's called a nasal core biopsy, and this is often referred to colloquially as a ram and jam procedure. And similar to the pinch biopsy procedure, you wanna measure in the same way to make sure you don't hit the brain.
So in this procedure, generally what we're using is sort of the rigid plastic sheath from something like the, the sheath over a, a true cut device, so the sheath over a a needle core biopsy device. That can actually be cut off at the end on a little tiny angle. And then again, often it'll be cut to fit so that there's no way, no matter how far you put it in that it can possibly reach any further than the cribiform plate.
And then this can be introduced and often you can get actually quite a nice large core of tissue out of this. So here's an example where we've actually cut our little plastic sheath to fit. Again, this is nice because it doesn't require any special equipment.
We're introducing it into the nose, and again, we've actually removed a, a beautifully large piece of tissue here, that can then get submitted for histopathology. Depending on the study that you pick up, it does appear that the likelihood of a diagnostic biopsy is somewhere in the 60 to 80% range. So one of the things that we do forewarn owners about is the possibility of a non-diagnostic biopsy.
And again, that could require that we go back and re-biopsy. It could require that we actually switch techniques, so maybe we would consider going back and doing a, a rhinoscopy in a dog who has a, a blind biopsy that's not diagnostic, for example. But again, sort of forewarning the owner about the possibility of a non-diagnostic biopsy is a very nice thing to do just so they're aware of the possibility that we may need to do more when we get our histopathology back.
So, assume that we have obtained a diagnosis of nasal neoplasia. What are some of the treatments that we would consider for this animal? So, palliative treatments, so, NSAIDs, steroids, intermittent antibiotics, things like that.
In a fairly large study that was conducted of dogs with carcinomas, median survival time was about 3 months with those kinds of palliative treatments. And again, we definitely do see dogs, especially dogs receiving NSAIDs, who do have to see, do seem to have some amount of reduction in their bleeding and reduction in their sneezing and things like that. So if you do have an owner for whom more aggressive therapy is declined, I unquestionably think that it's worth trying these kinds of simple things.
This is one disease where really there appears to be no real benefit to surgery. So going in there and trying to sort of scoop out everything that's in the nasal cavity, most of the studies suggest that there's really minimal to no benefit, to doing those kinds of procedures. So this does not appear to be a surgical disease.
What about chemotherapy? So again, I mean, we really like to use local therapies for local diseases like this. So it wouldn't be our first choice, but certainly there are plenty of places around the world and even here in the US where simply there isn't access to radiation therapy, or we may have an owner for whom that's just simply not possible, for travel reasons or cost reasons or anesthetic-related reasons or whatever.
So there are actually two case theories out of Australia that have looked at chemotherapy for the treatment of nasal tumours. And in both of these studies, actually the Protocol was a combination of daily oral paroxicam with alternating doses of doxorubicin and carboplatin at the standard doses that you would find in the, in the plum formulary or any other formulary. And again, these are given at 3-week intervals.
So doxorubicin 3 weeks later, carboplatin, 3 weeks later, doxorubicin, etc. And actually, the prescription that was reported in these two papers was to do 4 of each of those. So 4 doxorubicins, 4 carboplatins.
And again, it appears that about 3-quarters of dogs may have fairly significant improvement in their clinical signs and the median survival time actually in both of these studies was around the 8 month mark. So it does appear to be, you know, substantially better than what we observed with just, just palliative care, certainly better than with surgery. Not as good as, as radiation therapy, however, but a very, very reasonable thing to consider for an owner again for whom radiation therapy isn't possible, but they really do want to do something more specific or active to treat that nasal tumour.
Radiation therapy is the treatment of choice. And again, this does require a CT scan, at least for the sort of quote unquote curative intent or definitive type of radiation therapy that we like to offer. The classic treatment, we will talk about some advances here in a minute, but the classic treatment is between 2 and 4 weeks of daily treatments, occasionally every other day, delivered often Monday through Friday, again, sometimes Monday, Wednesday, Friday.
There are multiple, multiple studies that have actually evaluated sort of different little dosing schemes and different fractionation schemes and things like that of radiation therapy for nasal tumours, and this is something that's been done for 30 years. And really all of the studies result in very similar, outcomes, which suggests that the large majority of dogs will improve significantly as far as their clinical signs, probably 90% of these dogs will improve symptomatically. And if you put all the dogs together, the median survival times that are reported in the 12 to 18 month range.
And again, it's always important to keep in mind that this is a median, it's not a maximum, it's not a minimum, you know, technically, it's the halfway point. And in many studies, the two negative prognostic factors are dogs that have significant penetration of the cribiform plate or in some studies, other significant bony lysis and other bones, whether it's lysis of the the maxillary bones or the orbits or whatever. So dogs with extensive bony lysis, maybe on the short side of the average mark, and there are some studies.
That suggests that dogs who, whose tumours are read out as anaplastic carcinoma. So these poorly differentiated carcinomas, may have an outcome that's not as good as dogs that have the more traditional carcinomas like adenocarcinoma or squamous cell carcinoma, or those dogs that have, the sarcomas up the nose. So, these are the couple of things that may actually put a dog on the low side of the average mark.
Interestingly, to the extent that it's been looked at, nodal status does not appear to alter prognosis. So dogs with lymph node involvement appear to still have a roughly similar prognosis. However, again, that is information that we want because at least here at Colorado State University, our radiation oncologist will make sure that if we have a positive lymph node that that node is also treated with radiation.
In cats with, solitary nasal lymphoma, actually, the outcome can be really quite excellent with radiation therapy. So the, response rates are, clinically are bordering on 100% and, it's very, very common for these dogs, cats to have long-term control, so greater than 2 years of control. And I'll show you some statistics about that.
So here's actually a study that came out about 10 years ago now that actually looked at about 100 cats with nasal lymphoma that received a variety of different kinds of treatment. And sort of here's the take home message looking at this Kaplan-Myer curve, so we have disease-free survival on the, on the X-axis and the percent of patients that are still alive on the Y axis. And honestly, the patients who did the best numerically in this study are the patients who got radiation therapy by itself.
And again, if you sort of calculate down and look at the approximate median survival time, we're almost to 1400 days for those cats that got just radiation therapy. . Cats that got chemotherapy or cats that got a combination of radiation therapy and chemotherapy.
Look at survival times in roughly the year to 1.5 range. So again, similar to the dog story, if radiation therapy is simply not possible for an individual cat owner whose cat has nasal lymphoma, chemotherapy as we would use for other high grade, feline lymphomas is a very, very reasonable alternative.
Is it is good? Is it as specific? No, perhaps not.
But again, it's certainly far better than no therapy or palliative therapy with something like corticosteroids. So definitely something that's worth considering. So again, radiation therapy sort of comes in a couple of different flavours and, and the numbers that I told, told you previously about sort of almost everybody gets better, 12 to 18 month median survival times are using what we would call sort of curative intent type protocol.
So a relatively large number of treatments between sort of 10 and 20 daily treatments delivered Monday through Friday. Using some again sophisticated planning software and images obtained from radiation, I'm sorry, from CT scan to help plan where to put the radiation, etc. Etc.
But, the other kind of radiation that certainly has been investigated for these tumours is what's called palliative radiation therapy. So this is a less aggressive, a less focused form of radiation therapy where some radiation is shined down into the nasal cavity in sort of a less specific way, but utilising doses that are unlikely to do a lot of damage to the normal tissues in the area. And again, there are a few different protocols that have been looked at, so sometimes weekly treatments for 3 or 4 weeks, sometimes twice weekly treatments, etc.
And again, using this kind of palliative radiation therapy, which is really designed to address clinical signs, we do see most dogs have improvement of their clinical signs and the reported median survival times are in the 5 to 10 month range. So, about what you would see from chemotherapy. About half as good as what you would see with with curative intent radiation therapy.
But again, this is a simple form of radiation therapy. It's all outpatient, it often doesn't require advanced imaging. So again, if you have an owner who's whose travel constraints, don't let them do daily radiation therapy, whose financial constraints, don't let them do daily radiation therapy.
This certainly might be an alternative that's worth considering for sort of extended or durable palliation. So we do see some adverse effects from radiation therapy. And the most common adverse effects that we see are really related to the site where the radiation is put and that generally consists of excuse me, that generally consists of what are, what are called acute radiation effects.
So when these occur in the, on the mucous membranes, we use terms like moist desquamation or mucoussitis. So this is actually an irritation of the, the mucous membranes and in this case, the tongue, as a result of the radiation therapy. It's also common with some of the older radiation delivery techniques to also see car conjunctivitis Zika as a side effect, because of radiation to the lacrimal glands, which sort of obviously surround the, the orbit, and will often get a, a fairly high dose of radiation.
So, the acute side effects actually are side effects that generally will go away within a couple of weeks, and during that period of time, they could be a bit unpleasant. They may have some, thick ropey saliva, they may have some halitosis. They may have a bit of, of, gingerness when it comes to eating, so feeding, canned food, etc.
Versus dry food, etc. Can be helpful. But again, these are almost always self-limiting and and go away within a few weeks just with symptomatic treatment.
The chronic or cumulative late-term side effects that we can see following radiation therapy are a little different. And again, we can certainly see cataract and cataract development, retinal damage. And then we can also see things like permanent alopecia or leuka trachea as a result of, again, damage to the hair follicle cells.
So, obviously unilateral, cataracts and retinal damage, that's purely cosmetic as are these other skin changes. But, you know, there are certainly circumstances where we might actually see bilateral, ocular changes as a result of radiation to both sides of the nasal cavity. And that's something that could have some functional or quality of life related impacts and could need to be managed with things like haulsification, etc.
Down the line. So one of the things that I will mention is the newer radiation therapy machines that have sort of come out in the last 10 years or so, are much, much, much better at avoiding these kinds of side effects, both the acute side effects and the long-term side effects. And we'll talk a little bit more about that in a second.
So other palliative measures that can be considered, either if we've gone through radiation therapy or chemotherapy and those things have sort of stopped working or if we do have an owner who declines them. Are things like other anti-inflammatories, proxicam or other NSAIDs, steroids, etc. We've mentioned those already.
Intermittent courses of antibiotics can sometimes be useful. I generally don't recommend keeping these animals on consistent chronic antibiotics. But intermittent sort of pulse dosing of antibiotics to try and keep down any secondary infection can sometimes be associated with some amount of improvement.
And believe it or not, we certainly do have some dogs whose owners come in and present them for a repeat of their nasal flush, not for diagnostic purposes, but actually because it does tend to make them feel better after the procedure is performed. Again, reduction in the sneezing and the bleeding, less upper respiratory stridor, etc. So those are some palliative measures that can be considered.
So, One of the newer forms of radiation therapy that's now being interrogated for nasal tumours as well as a lot of other kinds of tumours or what's called stereotactic radiation therapy. And this kind of radiation therapy actually uses again a very advanced machine that allows us to deliver quite high doses of radiation to the tumour using a relatively small number of treatments. So rather than the typical 10 to 20 daily treatments, we're generally talking about between 2 and 5, in some cases between 1 and 5, daily treatments, but these are very, very large treatments.
And the reason that we're capable of doing this is that so the, the worry that we have if we sort of shine down radiation indiscriminately is these very, very large doses per fraction. Have the potential to do really unacceptable damage to the surrounding tissues, the skin and the bones and the eyes and the brain and things like that. But again, using very, very sophisticated, targeting technology, we're actually able to deliver a very high dose to the tumour in a small number of treatments while delivering very, very low dose to all the surrounding tissues.
And again, this really requires again some very sophisticated equipment. These patients have to be very carefully, meticulously immobilised so that they can be put in exactly the same position every single day. And again, it also requires some amount of onboard imaging so that the setup of the patient can be verified before each treatment.
So we know that they're set up exactly the same. And really one of the things that, that has allowed this to happen is the fact that you can shoot your radiation down from a much larger number of different directions. So it's sort of conventional radiation therapy.
Generally, you may shoot your radiation down from two directions, like one from the top and one from the side. And as a result, that can result in, in quite a large dose of radiation to things like the skin and the eyes and things like that. And the skin dose is actually outlined in red in this particular patient.
With intensity modulated radiation therapy or stereotactic radiation therapy, since you're shooting the radiation from so many different directions and actually, you also have a lot more control over the shape of the beam that's actually shown down onto the patient, you can minimise the amount of radiation that's delivered to the skin and to the eyes in a very nice way. And here's another example of that. So this is again looking at a CT image, three dimensionally through this patient at the level of the eyeballs.
So this is a 3D CRT plan where again the highest dose of radiation is, is delivered in red and that dose drops off over time. And with only a couple of different beams shooting the radiation therapy down, you can see, yeah, I mean, the nasal cavity is giving a nice big dose, but some of this eye is in red, all of this eye is in red, all the lacrimal structures around the eye are in red. And you can see that actually the heart palate is also getting a very high dose as well.
So you'd expect this dog to get some Fairly significant adverse effects as a result of this treatment, acutely, at least. But again, with the stereotactic plan, you can see you're actually able to carve off dose away from at least part of this eye, away from part of this eye. There's actually less dose delivered to the brain, and you're actually able to spare some, dose to the heart palate as well, especially the mucosa of the heart palate, and you can see a significant reduction in the amount of dose that's delivered to the head.
So again, this is a technology that's becoming more common in the States and I know there are some places in the EU that have it as well. So that's a question that you may want to ask if you're planning to refer a patient for, for radiation therapy is, you know, what kind of technology do you have? Are you capable of doing intensity modulated or stereotactic radiation therapy?
In which case, again, it could result in a smaller number of treatments and it will definitely result in a reduced incidence of side effects. So it's CSU, in these patients that, that receive stereotactic radiation therapy, it does look like we're seeing, average survival times that are about the same as what's been reported with more conventionally fractionated curative intent radiation therapy, about 400 days of median survival time. So again, unpublished information does it suggest that it's roughly equivalent.
So that's our little tour through nasal tumours in dogs and cats. And with that, we're actually going to move on, and discuss thyroid tumours quickly. So, I think a lot of us sort of think about thyroid neoplasia more often in cats than in dogs.
And in cats, again, thyroid neoplasia is something that occurs as a result of the fact that the majority of these tumours are functional and they produce thyroid hormone, and as a result, we run into problems related to hyperthyroidism. So I'm really not going to be discussing hyperthyroidism today, so that's a disease that's actually handled by our internal medicine specialists, not we in the oncology service because as we'll, we'll mention again, these are almost always caused by benign tumours in the thyroid that don't tend to cause any clinical problems related to the neoplastic mass itself. In dogs, however, it's actually quite the opposite in that about 90%.
Of the thyroid tumours that we see in dogs are malignant. So these are actually carcinomas and only about 10% are benign. So those numbers are almost flipped on their heads compared to what we see in cats.
And similarly, the vast majority of these tumours in dogs are non-functional. So only about 10% of thyroid tumours in dogs are functional, while about 90% are non-functional. So the complete opposite from cats.
So the majority of these are, arising from follicular cells, but we can occasionally see medullary thyroid tumours in dogs as well. Just like most other kinds of cancer, these are generally older dogs and there's no gender predilection. There does seem to be a breed predisposition for a few breeds.
Again, they're listed here. And again, there's at least one, family of malamutes that appeared to have, sort of a hereditary component to their disease. But again, in the majority of cases, we don't know for a fact that there's a heritable component beyond the breed predisposition.
How's a dog with a thyroid tumour likely to present at your practise? So the most common presentation is actually gonna be for an externally palpable mask. So something that the owner feels while they're petting the dog, or that you feel on your physical examination when the dog comes in for its yearly evaluation.
Sometimes the groomer will report it to the owner, etc. But there certainly are a few other things that we can see as well, so we can dogs present with cough as a little tracheal irritation due to the compression, or the pushing of the mass on the trachea. We can see change in bark.
We can sometimes see signs that might be consistent with laryngeal paralysis as a result of, damage or impingement of the recurrent laryngeal nerve, which kind of runs through the area where most of these thyroid tumours occur. And again, one of the things that we do try to impress upon the students when we, we teach them about this tumour type is this is a tumour type where we certainly can see, true thyroid tumours develop in slightly atypical locations. So if we remember back to our anatomy and embryology, we can actually see thyroid tissue, occurring in an ectopic location that can range anywhere from the base of the heart all the way to the base of the tongue.
And as a result, sometimes we will see mass effects in these other locations. That are that are diagnosed as thyroid, and that's completely believable based on the way that the thyroid develops during embryogenesis. And cats, again, the vast majority of them are adenomas and most of them are functional, and we aren't gonna be talking about about treatment of hyperthyroidism today.
I would say that in those rare cases where we do see a malignant thyroid tumour in a cat, our treatment approach would be very similar to what we're going to discuss about dogs. So, how are we gonna work up a dog with a thyroid tumour? So obviously the first order of business is a good thorough physical examination and we'll generally consider some baseline blood work.
Not too dissimilar from what you do in any other older dog where you're considering a workup for disease. We do generally measure thyroid hormone levels in these dogs, although again, the large majority of them are going to be normal or low. Again, a few dogs can have functional thyroid tumours, and occasionally they even present for clinical signs that are consistent with that.
And again, that could be important to know, for example, if we have a dog who's been chronically hyperthyroid, we might want to look at their heart before considering a major anaesthetic procedure to make sure that they don't have signs of hypertrophic cardiomyopathy, etc. Etc. We do like to evaluate the regional lymph nodes just like we do in most other kinds of tumours if we can feel them, to determine if there's disease there.
And then we do like to get some imaging of the thorax as well. So it does appear that about a third of dogs with thyroid tumours may have evidence of metastasis at the time of presentation, either to the regional lymph nodes or to the lungs or both. And it does appear that there are some things that we know about that can help to increase our or decrease our index of suspicion for metastasis at presentation.
So one of them is tumour size. So those tumours that are larger tend to have a higher likelihood of, of metastasis detection. Those tumours that are very fixed or adherent, at the time of palpation, just on a regular physical exam, they have a higher metastatic rate and dogs with a bilateral disease may also have a higher metastatic rate as well.
So, This, this thorough staging for metastasis actually is important. So if we do have evidence of metastatic disease beyond the regional lymph node, surgery is generally really a very, very little utility unless it's needed for palliation of some kind of clinical sign that the dog is having. So the best therapy for this disease if the disease does appear to be relegated to the neck and or regional lymph nodes is surgery.
And this kind of surgical procedure, is kind of variable in its complexity, largely dependent on the clinical presentation of the patient. So if we have a tumour that's mobile and relatively small, actually, removal of the tumour is a fairly routine, and, not a high risk procedure. And really when we're trying to assess mobility of these tumours, what I've been told by our surgeons is that actually it's very, very important to assess mobility primarily in the cranial caudal direction.
So does it actually move up and down in the neck? Almost all of these tumours will be mobile side to side, so moving from medial to lateral, etc. And that's because often you're moving the entire laryngeal apparatus and etc.
When you're moving side to side. But again, if they're moving up and down, that does give you an indication that the likelihood of serious complications with surgery is probably gonna be less. So it's certainly not a, a complete showstopper to consider surgery in a case that does have a or immovable thyroid tumour.
But, these are the cases where the risk of, of complications is higher. So these are the ones where we may be more likely to see things like significant haemorrhage, hypocalcemia as a postoperative, postoperative, complication, nerve damage, again from the recurrent laryngeal nerve and things like that that are running through the tumour. So these are the ones where again it may be more in the pet pet's best interest either to refer.
Or at least to consider advanced imaging prior to, surgery to really get a better sense about what structures may be involved, so the surgeon has a better sense of exactly sort of what they're getting into. There are some complications that we can see, however, and again, they do tend to be more common in those animals with the either bilateral or fixed tumours. And again, most of those are things that I mentioned already.
So haemorrhage, laryngeal nerve damage. In the bilateral cases, we certainly can see hypothyroidism. And in the bilateral cases, we can also see iatrogenic hypocalcemia.
So if during the the course of, of thyroid tumour removal, we managed to also remove all four of the parathyroid glands. That's an animal who's going to be hypoparathyroid and may require supplementation, either for a period of time or sometimes forever actually after surgery and those animals need to be watched very, very carefully postoperatively if you're concerned that you may have removed all four of the parathyroids. So the outcomes are variable again depending on the clinical presentation of the patient and some information that we get from surgery, but In an animal who does not have evidence of metastatic disease, and there's actually no evidence of vascular invasion either grossly, based on imaging or intraoperative inspection, or microscopically, the reported median survival time is in the neighbourhood of about 3 years with surgery alone.
And again, a, a caveat to that is there is a small subset of these patients who do have the potential to behave aggressively despite the fact that the tumour does not look particularly worrisome under the microscope. And again, it was Really movable, etc. In those animals who do have evidence of vascular invasion at the time of surgery, so either grossly or microscopically, even in this situation, their median survival time is around a year with surgery.
So, not the worst outcome, compared to a lot of other tumours that we treat. These are the animals where, where we'll consider medical therapy to try and delay or prevent metastasis. But unfortunately, we really don't have a lot of useful statistics about exactly how well postoperative medical therapy works for this disease.
Empirically, I tend to reach for carboplatin plus or minus a non-steroidal anti-inflammatory drug for these patients for post-operative management. And really the justification for that is the fact that we do know that we can see some big gross or unresectable or metastatic thyroid tumours shrink with drugs like carboplatin. So we intuitively think that we can kill some microscopic tumour cells that are left over after surgery in those patients.
But again, it is important to impress upon the owners that we don't have any meaningful statistics about exactly how well post-operative chemotherapy for this disease works. So, are there any other things that we could consider? So one of them is external beam radiation therapy.
So if we have a tumour that's unresectable, so it is so big or so infiltrated that it really can't be removed safely. Radiation therapy can actually be an excellent treatment, for this kind of tumour. But one of the interesting kind of facts is that this is a tumour that tends to shrink very, very slowly.
Following radiation therapy. So the median time to maximal shrinkage is about 10 months after surgery, I'm sorry, after radiation therapy. So this takes a long time to shrink.
but the outcomes can be actually quite good for these dogs with locally advanced non-metastatic disease with one report, about 80% of dogs being alive at a year after radiation therapy. So really an excellent choice to consider. Again, the older studies, for example, this one from 2000, do use the more conventionally fractionated.
Sort of everyday for several weeks form of radiation therapy, but just like with the nasal tumours, this is a tumour type where we are starting to do more stereotactic. So high dose per fraction type radiation therapy, although again, we don't have statistics sort of comparing its efficacy to the more conventional forms of radiation therapy that have been utilised in the past. So, again, chemotherapy is something that we can consider for patients with unresectable or metastatic disease.
Carboplatin is the drug I generally like to use postoperatively. Doxorubicin is another drug where we do occasionally see some evidence of anti-tumor activity. Most of the The activity that we see is fairly modest, so some small amount of tumour shrinkage or disease stabilisation for a period of time rather than complete disappearance of everything.
And again, generally, that's the kind of thing where if we do see improvement, it may last for 3 to 5 months, something else like that approximately. So one new tool that we do have in our arsenal where there's at least some anecdotal evidence that there may be some advantage to its use as palladia, the mast cell tumour drug that's sold by Zoetis. So there's a study that came out a few years ago that actually looked in a fairly non-scientific way at a variety of different kinds of tumours other than mast cell disease, where palladia was used as part of the, the tumour management.
And again, here's a few of those tumour types and as you can see, there are about 15 dogs with thyroid tumours who actually were treated with palladia either by itself or along with other things like a non-steroidal or metronomic chemotherapy, etc. And about a 25% of these patients actually had what the, what the investigators assessed as to be meaningful tumour shrinkage or partial response, and about another 50% had their tumour stopped growing for again, what they considered to be a clinically meaningful period of time. The average amount of time that these animals had their disease at least stabilised for if they fell into the 75% that was a responder, was in the neighbourhood of about 25 weeks.
So again, the neighbourhood of about 6 months. So it could be something to consider again for those locally advanced or unresectable cases. We tend to be fans of starting with sort of the conventional injectable agents here, just for, tolerability reasons, so they tend to be better tolerated than palladia.
But again, I do think that palladia is certainly somewhere on our list of things that we consider trying in those cases where, other things. Have, have not been effective. So definitely something to consider.
Here's just one example of a dog with a metastatic thyroid tumour who did experience some, some fairly nice tumour shrinkage after a few weeks of treatment with palladium. So again, it is something that certainly could be considered. And then a final thing that I'll mention very quickly, and again, we do get this question from owners quite commonly, is what about radioactive iodine therapy?
So this is the treatment of choice for many, many forms of human thyroid cancer. So, it's quite common for, for human thyroid cancer patients to be treated with radioactive iodine, also called I-131. And again, obviously, we have a lot of experience using I-131 to treat cats who are hyperthyroid.
So a logical question is, is this something that we could actually do in dogs? So, one of the things that you might say as well, but such a small percentage of these, these dog tumours are actually functional, would radioiodine even work? One of the interesting things is that these tumours don't necessarily have to pump out thyroid hormone in order to be able to take up iodine.
So there's a fairly high number of these thyroid tumours that appear to be non-functional that will actually still take up iodine. And generally, you need to do some nuclear medicine scans in order to sort that out, using either technetium 99 or iodine 125 to actually see if the tumour will sufficiently take up iodine. And then actually they utilise by they I mean like the radiation oncologist or whoever is doing this actually utilise that information.
To calculate how much radioiodine should be given to the patient for therapeutic reasons. And again, this is something that requires a high dose of radiation, delivered via the iodine compared to a cat tumour. And we can see some side effects from it.
So bone marrow toxicity is one thing that has been reported. So, the real downside from this, and this is incredibly variable from location to location is there tends to be a lot of variability in sort of the the radiation safety and radiation holding requirements following radioiodine therapy in dogs. So how long do they actually have to be held in the hospital, you know, under restrictive conditions after they receive that dose of radioactive iodine?
Again, around the world, it's actually been incredibly variable. I know there's some places where it can be as short as 5 days. At our particular institution, we actually do have a licence to do it, but it's more like 4 weeks because of the state regulations about how to handle these radioactive patients.
So this is something that again, depending on the circumstance, depending on where the where the pet is being treated, could be a consideration. And there are some fairly large case the primarily out of New Zealand that actually do suggest that this is a reasonable treatment option to consider for some patients and long-term control, even in patients with metastatic disease can be seen in some of these circumstances. So it could be a consideration depending on the circumstance of your patient and, and your localization.
And with that, I thank you very much for all of your attention, and again, I'm more than happy to answer any questions that come up if you would like to email me using the, the email address that you can actually rewind and see on the very first slide. And again, thanks very much for your attention. I, I hope you tuned into the next lecture as well.