Hello. It's Anthony Chadwick from the Webinar vet welcoming you to another episode of vet chat. And this is during our oncology mini series.
I'm really, really pleased to have Owen Davis on the line. Owen is the, head vet of the oncology service at Bristol Vet specialists. Which is a CV S practise.
Based on, funnily enough, in Bristol. It, it's always good, I think. Previously in in previous time zone and you couldn't actually say where you were based because it was deemed as advertising by the Royal College.
So the world has has moved on, hasn't it? But, it's really great to have you on, perhaps for those people who aren't familiar with you. And of course, they should be, because if they're listening to webinar vet webinars you, you've done many webinars for us and really appreciate your you help with those.
But for those who perhaps aren't as familiar, perhaps you could just give a little, intro, about your history, your back history as a vet and so on. Yeah, sure. Well, I've been a vet for almost 20 years now.
And in the first half of that I was a general practitioner, started off in, mixed rural practise, doing a lot of large animal work, and I progressed slowly into small animal work, working through charities for a few years and then a kind of progressive small animal practise. And then, in the last 10 years, I've been doing oncology referrals. I was a resident at the Royal Veterinary College for three years, and since then I worked at, High Croft referrals which, last year rebranded and moved to a new site and became Bristol vet specialists.
I'm now a registered specialist in oncology, in the USA UK and Europe and, lead a small team of one other specialist, two residents and a group of specialised nurses where we treat cancer and cats and dogs in Bristol. Oh, and I think it's, it's really interesting. Obviously, you came from a a GP background and that must give you a a sort of extra perspective, perhaps, than if you'd immediately gone into university and residencies and internships and then lecturing and so on.
What do you think that brings to you that sort of knowledge of of what GP life is like, Yeah, I think that's very helpful. I when people are trying to refer cases, often that they found very difficult. Or perhaps they felt they could have done with a bit more support in working up I.
I feel I understand that I feel I've been there. I also feel that, you know, fundamentally, I'm a vet. First and foremost, I may be an oncologist, but I'm first and foremost a vet, and I don't want to lose that.
I want to be able to triage an animal with a broken leg and provide appropriate analgesia and bandaging. For example. I'd like to think I could, work up and treat appropriately, an animal with heart disease or chronic diarrhoea, at a GP level, not trying to be a specialist or anything.
So I want to continue to be a good all round vet or as good as I can. At least I think also interesting at Bristol Vets, you multidisciplinary team. So that must also be useful that when you're seeing cases, oncology affects every single system, Doesn't it from the brain?
Neurology skin, obviously the the blood system liver. Gastro. So to have that, I suppose to people referring with oncology usually Or do you find that you're also getting a a throughput coming back from the vet to, you know, our referral vets in your practise as well, is it?
It's a two way street, presumably. Yeah, we we do get quite a few cases. For example, brain tumours, CNS tumours, often come through neuro first because they might present as an animal who's just seizuring.
And when when we started, I mean, seven years ago at High Croft referrals. I was the, first oncologist in the area, and a lot of people weren't used to referring to a dedicated oncology service, so we used to see a lot through medicine and surgery. Now, I think our surgeons now medics are quite pleased that a lot of the cases will come straight to us first, and we involve other disciplines where needed.
So probably 80 90% of what we see is straight to us, and another 10% is through other disciplines, like neuro ophthalmology, dermatology, et cetera. And obviously you did a master's, I think, around lymphoma that that is kind of our bread and butter tumour that if you like people in general practise, will will have a go at, I mean, have things now moved on. Should we still be treating, lymphoma in practise, or is it something that you would really recommend referring across as much as anything?
It's also the health and safety of drugs. We've got to be really careful how we deal with some of these drugs as well, haven't we? Yeah.
I. I think in principle, there's no reason why lymphoma shouldn't be treated in practise at all. That said it does take quite a lot of work behind the scenes.
As you said, we need to make sure drugs are being used safely and to use drugs safely, you need three things you need. The, the drugs to be drawn up in a fume cupboard. They need to be administered with a closed system transfer device to prevent spillage or aerosolization.
And you need chemo tested P PE like gowns and gloves and eye protection, et cetera. So those three things may sound daunting, but the fume cupboard doesn't have to be in your practise the fume code could be in someone else's practise. And there are services now that will be able to send you drugs, with a courier after drawing it up in their fume cupboard.
And there's more than one of those. And those services will also be able to provide close system transfer devices and P PE, so it's very doable, thanks to such businesses. The other thing you need to do in practise is make sure that people who are pregnant or nursing are excluded from administering or dealing with chemo.
They if we use the fume herds, the P PE, the closed system, transfer et cetera, then they shouldn't actually be any risk. But we're being built and braces, so we exclude people who are vulnerable, the pregnant and the nursing. And we need also to think about where in the practise the treatment is administered.
We don't want a large throughput of people walking. We want to make sure it's got all the IV stuff. We need all the stuff to remove the IV safely and all other drugs to be given around the same time, like Martin, so we don't want people running across the practise wearing P PE and running back again.
So it needs a little bit of thought and a little bit of planning. But it's otherwise very doable. There's various, recipes that can be used, you know, the the Chop protocol top protocol widely available, widely described.
And a lot of practitioners are, quite, well versed in In doing these has has sort of lymphoma treatment moved on, though, Or do you think we're getting better and becoming more personalised in the way that we treat it? Because we understand the biology of the tumours better? Because obviously lymphoma is a is a big term, and there's lots of different stages and types aren't there and so on.
No, you're you're absolutely right. Some lymphomas are very easy to treat others, extremely hard, and that underlines the fact that it's a group of at least 30 if not as many as 5055 different diseases. Lymphoma in that sense is a misleading term.
What we, should be doing in practise is recognising the lymphomas that are low grade and the lymphoma that are high grade, and most of the ones we see the typical dogs who come in with suddenly, very large lymph nodes everywhere. They're gonna be high grade diseases. But there are a significant minority that are low grade diseases, and these guys may not need treating.
They may might just be cases that you monitor, and you think about treating perhaps when disease is more advanced. The other thing with the common high grade disease is it's very helpful to determine who's a B cell and who's a T cell. And if you can, within that you can break that down to other subtypes of disease.
For example, a T lymphoblastic lymphoma is actually very aggressive tends to have a very sad prognosis. The other high grade T cell lymphomas are still very aggressive, but but less so. And some of the B cell diffuse large B cell lymphomas are these cases who may live for a few years in some cases and can do really well on on the chemo.
So knowing that prognostic information is useful not least for owner's peace of mind and preparation, but for planning the kind of treatment that's gonna be needed. Some of the T lymphoblastic cases benefit from a very aggressive treatment straight away. They're often sicker animals.
They might need hospitalising, for example. But some of the other sta substage a healthy B cell and T cell high grade lymphomas you could treat quite happily with a cough or chop protocol. There's some evidence now to support use of a different protocol in the T cell, high grade lymphomas.
And that's what we do in in our practise. We tend to use low muste based treatments like lock or plop compared to the traditional chop. The increasing support says that the, the chop protocol works best for the high grade B cell cases.
Talking about, T lymphocytes. It was one of my areas of interest as a dermatologist was epithelio tropic lymphoma and obviously was obviously a treatment there as well. Part of the problem also, is this reactive lymph lymph, lymphocyte compared with a neoplastic lymphocyte can actually be quite challenging for pathologists to recognise that.
And actually I had a a dog who had some lip fold pio derma or lip fold lesions, and I took them out and I decided to send them off to, Trevor Whitbread and he came back and said, Oh, this is epithelio Tropic lymphoma and my cases of epithelio tropic lymphoma used to be Oh, my goodness. You know, I referred to me, were really sort of, poor prognosis and usually fell apart within sort of 4 to 6 months on various treatments. But, the dog actually lived for several years and didn't really die of his epithelio trophic lymphoma.
So I think, as you say with all of these diseases, there is a big gradation isn't there of severe to, to very mild presumably. And those ones probably are not spotted because people notice a bit of redness to put them on steroids. And they actually do rather, well, just on that sort of intermittent treatment.
Yeah, I think epithelio trophic lymphoma is a really good example of a disease that's quite hard to study, because if you're studying these cases, you tend to recruit at the level of the pathology lab where all the biopsies get sent and you can get a list of the diagnoses with epithelio tropic lymphoma. But what that doesn't tell you is the severity of clinical signs and the proportion of surface area of the animal that's affected because you could have one really aggressive looking lesion histologically. But if it's just one lesion, it could easily be removed and the rest of the animal's fine.
And then you could get the animals that are just bright red. And no amount of steroids or other treatment will control their pruritus and their clinical signs and histologically. They might look very similar, but one is actually much more advanced than the other, and it's even on clinical notes.
It's very hard to quantitatively say how much the animal is bothered by this or how much surface area is affected. And I agree. We I mean, there's a couple of good studies now that have shown that the lip fold PMA the kind of mucosal, epithelio tropic lymphomas that don't affect the skin.
We usually do a bit better than the ones that are multifocal or ones that have a large amount of skin affected. Fantastic. Where would you say that the sort of big advances are in oncology with regard to the some of the screening tests that we're seeing?
Are they proving to be useful for you now? I have I have to say I haven't used any of these liquid biopsies or other tests, that are currently being rolled out myself. I think potentially, they could be very useful because, dogs and cats are tough and stoic or with with with a few exceptions, that we all know of, I'm sure.
But generally as species, they don't tend to tell us much you or I might go to the doctor if we're feeling a bit weird or something's not quite right. And to be able to detect a lot of cancers in cats and dogs they present when advanced, the value of the yearly, health check is is is great for a lot of things, but for detecting cancer, the sensitivity is quite low. It's only 4% of cancers or something like that are detected at a yearly health check.
8% of cancers are detected, incidentally, and pretty much all the rest of them are detected at quite an advanced stage when the animal is presenting with clinical signs. And I think we all have experienced times in practise when we thought I had no idea this was going on. But we have a very, very advanced cancer now If only someone could have accidentally x-rayed this dog a few months ago, we might be able to do more about it.
For example, an osteosarcoma, presented when pretty much all the bones have been destroyed. And you can think of all the micro metastatic disease burden the dog's gonna have Or a hemangiosarcoma that presents with a hemo abdomen or the anal gland tumour that presents with disseminated disease. Or at least it's very large regional lymph nodes and the dog can't, defecate.
If we could pick them up at an earlier stage, it would be a better prognosis and much more affordable for our owners to to deal with these things. So, I, I can really I really applaud the idea of trying to be able to screen for these things and pick them up sooner in There's lots of different screening tests available. Some of them use micro satellite DNA.
Some of them use, next generation sequencing. Some of them have, looked at using nucleus sonics. But the the premise is that cancer cells are very easily broken.
And, where there is a tumour, there'll be cells breaking, releasing molecules into the circulation. And as it happens, DNA tends to be a very, very stable molecule, one of the most stable molecules in the world. And so you could do a blood test to check for floating bits of DNA from a tumour.
Some of the data I've seen so far has got some very impressive results. But when you break it down into the tumours that I'm mostly interested in picking up early the osteo SARS, the heio SARS, the sensitivity for them is perhaps not as amazing as I'd like. And the sensitivity for some tumours, like mast cell tumours that are more obvious and can be found on a skin exam, is actually higher.
And that tends to pull the data up. But there's lots of different companies working on it, lots of different techniques, and it is getting better year on year. So I think in the future, just like the screening tests for, prostate cancer in men, I think this could become much more useful.
I think it's one of those things. If you don't start on a pro, then you're not going to improve. So start somewhere, don't you?
With a test that perhaps isn't ideal but has some use, and then develops, you know, with time and with usage and so on. You were you were talking about the ideal treatment for an osteosarcoma because there was always a lot of controversy about, you know, drugs like cisplatin. Do you amputate, don't you?
Et cetera, et cetera. So where are we at with, with some of these bone tumours? Yeah, with with osteosarcoma.
I tell my clients we need two treatments. Really? We need one to deal with the local disease and the pain.
And we need a second one to deal with a metastatic disease. And, you know, even at a small size, a very small size, we'll have to assume that the primary tumour will have seeded lots of microscopic, mets, often in the lungs. But it could be lymph nodes or other bones.
So we need a local treatment, and then we need a systemic treatment. Basically, because of the advanced stage at which most osteo SARS are picked up, amputation is usually the mainstay of local treatment. And because of the spread to other parts of the body, chemotherapy has to be the mainstay of treatment there now there.
There's a lot of, research going on into osteosarcoma because it's a very good model for paediatric bone cancer and, one, particularly in terms of controlling metastatic disease. There's been a lot of interest in finding an immunotherapy. Osteo SAR is a very immunogenic cancer, so there's a lot of interest in trying to wake up the immune system to try to target it.
And so there's been some interesting data published so far, either with chemotherapy or just as a sole immunotherapy. I'm afraid I'm not aware of any of these immunotherapies that are available commercially, and some of them have had quite, marked adverse effects. So you know that resulted in the project being, put to one side.
But at some point, we will hopefully get a useful immunotherapy that can be used either instead of or as long as with, along with chemotherapy. For these and so for, for you and me in our practises. At the moment, the mainstay of systemic therapy would either be carboplatin, which is much, much safer than cisplatin, much kinder to the kidneys, usually a very well tolerated drug or you could use doxorubicin, which is just as good, but more likely to cause diarrhoea.
And in some dogs there's a risk of cardiotoxicity, and that would be the mainstay with regard to the local disease. As I said, amputation is the main thing if we can, if we can't do amputation and palliative radiation therapy is a very good way of not treating the tumour but killing those, those pain receptors, if you like, and making the leg much more comfortable. And there is, a company called Bio of Vets who have introduced a, Cemental plasty product, which is where you've got a load of dissolved bone due to the tumour, you can inject into the tumour a a bone cement, which will kind of hold things together.
And they claim that it has been able to stabilise the bone and, also reduce the associated bone pain with a gross osteo sar. Now I. I would always try to amputate if we could.
But for those few cases important few cases where amputations, not appropriate things like palliative radiation or the cement plasty may be, may be very useful. Obviously, Buddy's here, he's he's feeling that you're talking too much about, dogs. So have you got anything you wanna tell him about cats that he should know?
Cat cats are brilliant because the the more we we learn about oncology or veterinary medicine in general, the more we realise cats are different. And if we're talking about lymphoma like we were a minute ago, it's remarkable how, difficult The prognosis with feline lymphoma can be to predict. People have looked at all kinds of clever ways of trying to gauge prognosis, and the effect has been shown to be quite weak.
And people might intuitively think that if a cat is very, very poorly at diagnosis, their prognosis would be much worse. And that's certainly the case for dogs, But But it isn't necessarily for cats. The only thing that tells us if a cat is gonna do well on treatment for lymphoma is response to treatment.
Regardless of what treatment you use, that doesn't matter so much. I would look to restage them, image them thoroughly after three or four weeks and ask the question, Have we got a complete response where the disease is vanished, or have we got a partial response where the disease is reduced, but still you can find it. And if you haven't got a complete response, I would look to change treatment to try to make sure that we do get that to give them every chance of getting that complete response.
And some of these cats who are getting into a complete response quickly, they they'll live for several years. Yeah, and against all the odds, you might get a renal and CNS and, gastrointestinal lymphoma all at once. And the cat's really poorly, and the owner's almost gonna put them to sleep.
But you thought you might try treatment, and within a month they're much better. And you're you're still seeing them for vaccines two or three years later. Fantastic.
And what sort of are you using for, lymphoma? Personally, I start with the the traditional cop protocol because no one's been able to definitively show that anything's better than that. If my cat isn't responding so well, I'll make it a chop protocol.
Or, I might add in low muste. If costs are an issue and make it a lock protocol, just adding more agents gives them more chance of a complete remission. Fantastic.
Just a final thought on antibody therapy. You know, you you mentioned it with the immunogenic treatment. Obviously difficult at the moment in the UK cos of the whole cascade system.
But I know more of that is going on in the States, isn't it? Yes. Now, that's some really exciting.
Advances have been made in the last few years because the, antibodies humanised antibodies have been used in human medicine for some time alongside chemotherapy, often to target cancer with specific mutations, specific genomic patterns. And we're we just haven't got the funding to be able to do that on a widespread basis. But there are a few things coming along the line which I'm very excited to, to see rolled out into the UK.
One of these, is a drug called Gil Gil vet maab, which I believe is made by MS D and currently has conditional licence from the USDA in the States. Now, this particular drug is a canine. Hear that canine monoclonal antibody.
So we have a minimal risk of anaphylaxis or hypersensitivity because it's a special dog antibody, against an immune checkpoint and one of we realised recently that the job of doing well in cancer treatment is not just killing cancer cells. Cancer cells are the body's own cells, and if you kill enough of them, you'll often cause a hell of a lot of collateral damage with the body's own cells. The the often the secrets in getting a really good outcome for a cancer is getting the immune system on side.
Getting the immune system to recognise these cell cells that have been flying under the radar and causing all kinds of damage. And the the way that has become quite popular of trying to modulate the immune system is by modulating these immune checkpoints we immune. Making an immune response is often a very finely balanced decision that the immune system has to make because you don't want inflammation going on all the time.
You'd get unacceptable and life limiting immune mediated disease. At the very very least, you'd get inappropriate inflammation that would get in the way of wound healing and epithelialization of just a a cut or something. So the immune system has to say what definitely needs to be, addressed and what doesn't and when to start and when to stop.
And it's a very finely tuned thing, and it does this well. One of the mechanisms by doing this is these immune checkpoint molecules. It, I guess it to make an immune response.
The immune system needs enough evidence from the cytokines or the cellular damage or the cellular background to say that immune immune response is needed. And the cancers are very, very clever. They will often produce molecules that will specifically address these checkpoints and turn off the immune response.
So, Gil VTM a. And, and other antibodies that have been used like it will bind this, receptor on the T cells and prevent it from being inactivated by the cancer's ligands. And it means that an immune response that would otherwise be turned off is allowed to proceed.
So that's very, very exciting. And in the USDA we've got, they have con con what's the word conditional licence for treatment of melanoma and mast cell tumours at the moment, fantastic. It's great to see that, as always, medicine continues to advance.
But oncology has had such a massive advancement when you think you know, human and animal over the last 2030 years. And, yeah, really interesting to hear about these more, very much more, targeted and personalised treatments as well, Which is W? When we were treating with prednisolone alone, it was a bit sort of hammer.
You know, a sledge hammer against a small nail, wasn't it? Cos it doesn't just affect the tumour. It affects everywhere else as well.
Yes. Yeah, absolutely. Yeah.
Owen, thank you so much for, coming on. It's always interesting to, to hear what's going on in the oncology world. And, hopefully we'll, we'll see you soon on another podcast or webinar very soon.
Yeah, Should do. Thanks ever so much for inviting me. Thanks, Owen.
Thanks everyone for listening. This is Anthony Chadwick for the Webinar vet. And this has been vet chat.
And we hope to see you very soon on another podcast or webinar. Take care. Bye bye.
