EPISODE 193 | RELEASED November 21, 2022
Best Treatment for Early Oral Melanoma in Dogs | Dr. Brooke Britton
Oral melanoma is an aggressive cancer, but catching it and starting treatment early can yield good results.
Marjorie called in to our Listener Line to ask what the best treatment options are for early oral melanoma. Oral melanoma is an extremely aggressive dog mouth cancer, but catching it early does present some good options for treatment.
Oncologist Brooke Britton explains how the location of a melanoma tumor can change prognosis, as well as the factors that can impact the success of a surgery. She then talks about the melanoma vaccine, and tells an amazing story about one of her patients who had a miraculous recovery.
Links Mentioned in Today’s Show:
ONCEPT Canine Melanoma Vaccine https://www.petcancervaccine.com/vaccine
[00:00:00] >> Dr. Brooke Britton: And his person decided to give the vaccine, just to hope that it worked, because it was benign. And we gave a low chance that a tumor was going to respond, and that dog actually had complete shrinkage of his tumor.
[00:00:15] >> Announcer: Welcome to Dog Cancer Answers, where we help you help your dog with cancer.
[00:00:22] >> Molly Jacobson: Hello, friend. Today on Dog Cancer Answers we have a call from our Listener Line. Marjorie called in to ask about how to follow up on treatment options when you catch oral melanoma early. To answer her question, we’re joined once again by veterinary oncologist, Dr. Brooke Britton. Thanks for joining us today, Dr. Britton.
[00:00:42] >> Dr. Brooke Britton: My pleasure.
[00:00:43] >> Molly Jacobson: Let’s listen to Marjorie’s question.
[00:00:47] >> Marjorie: Hello, my name is Marjorie and I’m from Vero Beach, Florida, and thank you very much for doing this. My question is, what are the best treatment options when oral melanoma is detected early. I.e., there are no mets, and a small visible growth is seen. Again, thank you very much.
[00:01:09] >> Molly Jacobson: This is one of my favorite kind of callers into Dog Cancer Answers, someone who is calling in to ask a question on behalf of her earlier self and other dog lovers so that they can avoid going through what she went through, where she very kindly called in to say, This is the question I would’ve had if I’d been able to ask it at the time.
[00:01:30] >> Dr. Brooke Britton: Yes.
[00:01:30] >> Molly Jacobson: So thank you, Marjorie. It’s just so generous of our listeners to contribute questions for other people. So her dog, oral melanoma, very small, but visible growth, no metastasis. What do we have to tell her? What do we do for early detection and early treatment?
[00:01:50] >> Dr. Brooke Britton: Yeah, so early detection is very important for most cancers, I would say all cancers, but for melanoma in the mouth in particular. Oral melanomas tend to be very aggressive with a high metastatic rate, and they’re also very locally invasive, meaning that the tumor can infiltrate the underlying tissue and even the jaw bone depending upon where it is in the mouth.
So, the more towards the front of the mouth these tumors are, and the smaller they are, the better chance we have at removing them and hopefully extending a dog’s life significantly. We struggle to cure many of these tumors because of their degree of aggressiveness, but it is possible to have long term survival and a great long term outcome if we catch things early.
There is also a subset of small, what we call well differentiated or apparently low grade, less aggressive melanomas that happen in the mouth, and we think that there’s a subset that actually can live for years and years and years with surgery alone. But even for those less metastatic oral melanomas, we need to be fairly aggressive with how we deal with the tumor in the mouth.
Many times, rather than just shaving the tumor off with a scalpel or with electrocautery or laser, we need to actually remove teeth and bone underlying the tumor. And this is one tumor where, if we can, it’s very helpful often to do advanced imaging like CT scan to understand the extent of the tumor.
Many of these dogs have bony involvement of their tumor and we don’t really appreciate that when we look at them or we can’t see it on an x-ray because an x-ray is not as sensitive a test, and maybe it’s very subtle. So oftentimes, the advanced imaging like CT scan will pick that up. And oftentimes the margin that we need, so the amount of tissue that we need to take, is a lot bigger than we often think it is looking at the tumor.
So these tumors will extend past the footprint that we see. Kind of like the iceberg principle where the tumor that we see may be the tip of the iceberg.
[00:04:13] >> Molly Jacobson: Oh no.
[00:04:13] >> Dr. Brooke Britton: And we often need to take bigger margins than we think, more tissue than we think, to try to guard against tumor recurrence. But if the tumor is very small, you know, maybe a couple millimeters, for example, and we catch it very early and it’s in the front of the mouth, these dogs can do very well in the longer term. If the tumor is larger or it’s towards the back of the mouth, just because it’s harder to access back there, or if it’s on the palate, for example, that can be harder to deal with those tumors in terms of getting a surgical margin.
And because the tumors tend to be more highly metastatic, we will often recommend something post-surgery to try to guard against the tumor spreading, even if there’s no metastasis at the time it’s diagnosed. And usually that’s some form of immunotherapy like the melanoma vaccine.
[00:05:05] >> Molly Jacobson: Okay, great. So talk a little bit more about the melanoma vaccine, ’cause I know that a lot of people have been using it since it came out. So what do we know about it now that we’ve had some clinical experience?
[00:05:19] >> Dr. Brooke Britton: Melanoma vaccine has been out for several years and it’s a really nice option for these dogs and we know that it can statistically prolong life and improve the outcome in many of dogs with oral melanomas beyond surgery alone, particularly the low to mid-stage dogs. It’s more difficult for the vaccine to have a long-term effect or positive outcome in dogs with very late stage metastatic disease, as with many cancers, but there are still responses that you can see even in, in those cases.
And what it is is a DNA vaccine. We use a fancy word for it, we call it a xenogeneic vaccine. What that means is that it’s actually a human DNA vaccine, we’re giving a human protein called tyrosinase to the dog through the vaccine. And tyrosinase is expressed by melanoma cells. The beautiful thing about the vaccine is that because we’re giving a human protein, when the vaccine’s given, the dog immune system recognizes this as foreign and it builds antibodies to the human protein that they receive.
But the genetic code of the human and the dog protein are similar enough that the immune system starts to cross-react to the dog protein, and so it basically wakes up the dog’s immune system to pay attention to these cells. You know, cancer cells have a good way of doing what we call cloaking themselves. It’s almost like the invisibility cloak in, in Harry Potter.
[00:06:55] >> Molly Jacobson: Uh-huh.
[00:06:56] >> Dr. Brooke Britton: They just kind of mask themselves from the immune system. Kind of the nothing to see over here approach.
[00:07:02] >> Molly Jacobson: Uh-huh.
[00:07:02] >> Dr. Brooke Britton: And so what this does is kind of have an immunologic bait and switch. It tricks the immune system into waking up and paying attention to these cells, and then it seeks them out and targets them for destruction. Just like any other vaccine though, in any species, some dogs respond better to it than others. Some dogs build antibodies robustly, and others don’t, and everything in between.
And there’s not a good bedside test to measure which dog has really great antibody response and which dogs don’t. But it is a well tolerated vaccine with virtually no side effect. And so it’s a relatively benign thing to recommend, but if a dog experiences a benefit, it could be significant. It’s best in what’s called the microscopic disease setting. So when we have surgery and we’re worried that maybe there’s metastatic potential, but we don’t see evidence of it yet, that’s the best time or scenario to use the vaccine.
But I have seen responses in what we call bulky tumors, so tumors that are non-surgical or they had surgery and they’ve come back, so a tumor that we can see or feel. The vaccine sometimes can cause shrinkage of those tumors. And we all have stories like this, but the best response I’ve ever seen with it was an older Basset Hound with a very large melanoma on his palate. He was older and had other medical problems, and we weren’t going to do invasive or definitive treatments to try to deal with that tumor.
There was no evidence that the tumor had spread when we staged the dog and his person decided to give the vaccine just to hope that it worked, because it was benign. And we gave a low chance that the tumor was going to respond, and that dog actually had complete shrinkage of his tumor. And two years later – he was kind of lost to follow up after his initial vaccine series, and two years later I got a very nice note saying, Hey, the tumor’s gone, with a picture of a very happy dog. And, um, that dog had done very well in the long term.
So that’s not a typical response, but it just goes to show you that the immune system is a, a weird and wonderful thing, and sometimes immunotherapy, even by itself, can be very, very effective.
[00:09:21] >> Molly Jacobson: So he didn’t get surgery, he only got the vaccine.
[00:09:24] >> Dr. Brooke Britton: No.
[00:09:25] >> Molly Jacobson: That’s amazing.
[00:09:25] >> Dr. Brooke Britton: He had a fist sized melanoma on his hard palate and he was having a very hard time breathing and eating with it. And we talked about quality of life and whether or not euthanasia was the right thing for this dog, and I would’ve supported that, but his person wanted to try the vaccine just to see what would happen. And he had a very rapid response, which is not typical.
Most dogs take several weeks to a few months to build up an antibody response that’s more robust if they’re going to have that happen at all. So this dog had a really beautiful response. And again, it’s, this is not a typical outcome-
[00:10:05] >> Molly Jacobson: Right.
[00:10:05] >> Dr. Brooke Britton: -but yet it just goes to show you that these things can work. And happily with the melanoma vaccine, there’s really no downside aside from potentially the cost of it to trying it because the side effect profile is minimal to none. And um, so many of these dogs, I will end up recommending the melanoma vaccine even if the tumor appears to be less aggressive on biopsy, because the metastatic rate is generally high and the risk of doing the vaccine is minimal to none.
[00:10:34] >> Molly Jacobson: I don’t know if I’ve ever heard anybody talk about side effects from the melanoma vaccine in any of our support groups or in any feedback I’ve ever heard. So it’s very safe to give and it can really help.
[00:10:49] >> Dr. Brooke Britton: It can. It’s very safe to give. A little bit of inflammation or redness sometimes, or maybe a little bruise at the site of administration if we have a very small dog or a cat with thinner skin, or a rabbit, for example – we give these in rabbits, we give them in horses. So there are some cross species applications too. I know we’re talking about a dog here, but the melanoma vaccine can work in different animal species as well.
[00:11:15] >> Molly Jacobson: Well that’s beautiful.
[00:11:16] >> Dr. Brooke Britton: But even in a small, thin skinned dog, most of the times these vaccines are very well tolerated and they take five minutes to get their vaccine if that, and then they get up and go about their business, and it’s a very low maintenance therapy to give.
[00:11:29] >> Molly Jacobson: Wonderful. Let’s take a short break and hear from our sponsors. And then when we return, I wanna ask about the risk of metastasis in oral melanoma.
We’re back with Dr. Brooke Britton.
So in terms of a small, visible, towards the mouth, hopefully caught early oral melanoma, surgery, melanoma vaccine, generally, can you assume that spread has happened already with these? So I know sometimes we do assume that spread happens on diagnosis. Is that true of these oral melanomas or do we feel like we’re probably okay as long as we can get it all out?
[00:12:10] >> Dr. Brooke Britton: If the tumor is very small, you know, and usually we’re more encouraged by tumors that are under two centimeters, although two centimeters is still a pretty decent size, especially if we’re talking about a smaller dog, so, if we’re talking about on the order of maybe a few millimeters, very tiny, like a small mole size, for example, and we do a proactive surgery and we follow up with the vaccine, long-term survival without metastasis is absolutely possible.
Some of these dogs will never metastasize. I think I may be a little bit skewed or biased in my feeling about these tumors as well because they do tend to be more aggressive and usually when a dog is coming to see me, or a cat is coming to see me, with melanoma in the mouth, they tend to be larger tumors that are either non-surgical or we have more limited options. But these tumors can also grow very quickly.
They may appear as a small, pigmented, nothing concerning in particular, lesion, and then they may turn into something much more concerning very quickly. But to your point, some of these tumors are indeed less aggressive, and if they’re proactively managed, they can either be cured or if not cured a very long term outcome without any issue.
[00:13:26] >> Molly Jacobson: Would you typically use chemo for a small melanoma at this point, or do you use the surgery and vaccine as the first treatment options, and then…?
[00:13:34] >> Dr. Brooke Britton: Surgery and vaccine would definitely be the first treatment options and really standard of care. Chemotherapy can be used for melanomas, but it’s not very effective.
[00:13:42] >> Molly Jacobson: Okay.
[00:13:42] >> Dr. Brooke Britton: You know, most of the times we’re using maybe a drug like carboplatin, for example, which is an injectable chemo, there are others that have been reported, but chemotherapy is not typically very effective for melanoma. It has its place, but the response rates are usually under 20 to 30% and usually partial response.
So I will use it with dogs that have recurrence or metastasis of their tumors, or if we’re kind of getting down the line trying other things and the tumor is coming back or progressing, but it’s not a first line treatment for them.
[00:14:18] >> Molly Jacobson: Okay. Well thank you so much Dr. Britton. I really appreciate you joining us today.
[00:14:23] >> Dr. Brooke Britton: My pleasure. Absolutely.
[00:14:27] >> Molly Jacobson: And thank you Marjorie for calling in with that excellent question. Listener, if you have a question you’d like answered on the show, you can reach our Listener Line at (808) 868-3200 and leave a message. I’d also like to invite you to join our online support group, Dog Cancer Support. It’s a wonderful community of dog lovers who all understand exactly what you’re going through. You can find that at dogcancersupport.com.
I’m Molly Jacobson, and from all of us here at Dog Podcast Network, I’d like to wish you and your dog a very warm Aloha.
[00:15:08] >> Announcer: Thank you for listening to Dog Cancer Answers. If you’d like to connect, please visit our website at dogcanceranswers.com, or call our Listener Line at (808) 868-3200. And here’s a friendly reminder that you probably already know: this podcast is provided for informational and educational purposes only. It’s not meant to take the place of the advice you receive from your dog’s veterinarian.
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