Panacur for Cancer in Dogs │ Dr. Nancy Reese #109

>> Dr. Nancy Reese: Until you've been affected either in your family or your own pet, as a vet, I would like to have solid proof of everything. I want the studies to be perfect, and I want there to be no side effects. And I want to guarantee that X, Y, or Z will work. But when you're on the other side of that, trying to help your four-legged or two-legged, the family member with cancer, you're willing to look at all sorts of things that might help, especially when the standard of care isn't great. 

>> Announcer: Welcome to Dog Cancer Answers, where we help you help your dog with cancer. Here's your host, James Jacobson. 

>> James Jacobson: Hello friend. And thanks for joining us today for one of our Question and Answer shows. Today's caller, Sandy, has a really interesting question about using a drug designed for a totally different purpose, de-worming, to treat her dog's cancer. And joining us to address this outside-the-box idea is our resident medical editor, Dr. Nancy Reese. In addition to being a practicing veterinarian, Dr. Nancy has a PhD in epidemiology. And that makes her an expert sleuth when it comes to decoding scientific studies. Dr. Nancy is the chief medical editor of the sponsor of this show, The Dog Cancer Survival Guide, the amazing book written by Dr. Demian Dressler and Dr. Sue Ettinger, who you may know as Dr. Sue Cancer Vet. You can pick up a copy of the book on the website, DogCancerBook.com. 

And now let's get to our caller, who's been kind enough to leave a question on our Listener Line, which you can call at (808) 868-3200. Do that anytime you want. I'll tell you more about that later on, but first Dr. Nancy, thanks for being with us again. 

>> Dr. Nancy Reese: It's a pleasure to be here. 

>> James Jacobson: We're going to go back into the proverbial listener mailbag slash hotline, and take a call from Sandy about a dewormer drug called Panacur. 

>> LL Caller - Sandy: Hi, this is Sandy in North Carolina and my dog, an Aussie, was just diagnosed with stage 4A lymphoma.

And I was just wondering if Dr. Dressler has ever heard of using the dewormer Panacur for treating the cancer. There's conflicting information out there. And just wondering if there's been any success stories or possibly if there's a problem that it could actually cause the cancer to grow, which some people I've spoken with have said they've had that experience.

Thank you. 

>> James Jacobson: Well, Dr. Nancy, using a dewormer as a cancer treatment, I wasn't expecting that. 

>> Dr. Nancy Reese: So this gets into a pretty fascinating subject, at least for a nerd like myself. There are a lot of drugs that they're repurposing for use in cancer. Some of those are actually mentioned in The Dog Cancer Survival Guide, but fenbendazole, which is what Panacur is made of, is a really interesting one because who would ever think that something that we give to get rid of worms could possibly help at all in the treatment of cancer. And I have to admit, I don't have any personal stories of success or not success with it, but I have certainly looked into the use of it and how this came up about-- especially having family members with cancer -- I've been looking for all sorts of other repurposed drugs that might be in the arsenal for later down on down the line.

And the same thing applies to dogs as well. So as far as I could find that, I think the studies that first suggested this went back to the early 2000's, and they were doing studies in mice and injecting, I think lymphoma types of cells in these mice. And they found in some of the mice that cancers wouldn't really take hold.

So they couldn't then do whatever study they were doing on the lymphoma. And what they determined was that the mice that weren't getting the lymphoma to develop, they were treated with the dewormer fenbendazole for some, I'm not sure why they were de-worming the mice, but that seemed to be the critical thing that kept these cancers from taking a hold of the mice. So people started looking more at what this agent does and how it might affect cancer. And it comes down to, it affects little things called microtubules, which are important for supporting the cell and potentially making them grow and spread. And the fenbendazole tends to inhibit that.

And in worms, it affects them much more, but in cells that are cancerous, they also have a very high growth rate. So the fenbendazole, it affects their microtubules more than they would normal cells. So it's not going to be a cure-all for cancer that's for darn sure. But given that it started out in these mice, people started really thinking, well, what if we started using this in other cancers?

So there are anecdotal reports out there of people using dewormers and having their cancer somehow get better. But there really isn't a lot of great studies on whether this is going to be a good thing or not. We really don't know about the long-term side effects in humans. For dogs that were deworming, you know, we may give it for three to seven days, not continuously, like you might have to for a cancer type of treatment. So it's certainly an interesting factor. It won't be a cure for a lot of cancers. But we may find that it's some sort of adjunct down the line that combined with something else, it will make a different drug, more effective or something along those lines.

One of the mouse studies they found if they mice got fenbendazole plus vitamins, then the cancers decreased. But if they were given either the vitamins or the fenbendazole alone, or maybe it's just the fenbendazole alone, the cancer actually got bigger. And so that is, I think, where some of the, "it causes cancer" or "it cures cancer" came from, is that it was one combined it with vitamins and one didn't.

But then other people said that the mice, that their cancers grew, were kind of outlier mice, that, that didn't happen in the whole group. So you have to really pick apart the study to see that it's not universal effect. It's not "all the mice that got fenbendazole didn't get cancer" and "all the ones that got it, you know, the cancers grew and things."
So it's an interesting topic, but it's not, in my opinion, going to be the radical cure that we'd all like to have. 

>> James Jacobson: Sounds like there are definitely some off-label uses for this dewormer and a lot more research needs to be done. 

>> Dr. Nancy Reese: Yeah. 

>> James Jacobson: But I'm impressed that you're looking at this, not just for dogs, but for family members.
And I mean, this is what vets are doing. They're looking at all the options that are available and sometimes these drugs may have some therapeutic benefit beyond what they're intended for. 

>> Dr. Nancy Reese: I think that's a really good point because until you've been affected either in your family or your own pet as a vet, I would like to have solid proof of everything.

I want the studies to be perfect and I want there to be no side effects. And I want, you know, to guarantee that X, Y, or Z will work. But when you're on the other side of that, trying to help your four-legged or two-legged -- a family member with cancer,  you're willing to look at all sorts of things that might help, especially when the standard of care isn't great. So we have some of these cancers in dogs in particular, we just don't have good outcomes. And so, you know, the standard of care is great, I mean, things like lymphoma that chemotherapies are really pretty effective. But you get some of these rare cancers and you really start looking outside the norm to see what else can be done.

And that's where some of these repurposed drugs really come into play. 

>> James Jacobson: Dr. Nancy, thanks for weighing in on this. Thank you so much for being with us today. 

>> Dr. Nancy Reese: Thank you again. 

>> James Jacobson: Well, friend, that is it for today. To access the show notes for today's episode, go directly to DogCancerAnswers.com where you can also listen to or download any of our previous episodes.

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