The usual way we have used chemotherapy, in both human patients and dogs, brings about toxicity risks that can be frightening for many.
This fear is a rational one.
The reason that the bad effects of chemotherapy are seen is a bit complex, but stems from what I believe are two main areas.
First, the usual strategy in using chemotherapy drugs has been to give the MTD, or the Maximum Tolerated Dose. This translates into the idea that you give as much drug as you can up to, but not reaching, the point where it could cause heavy-duty side effects.
So when we give MTD’s, due to the fact that not all patients are the same, a fraction of them will experience the serious and sometimes even life-threatening consequences. These are the sensitive ones.
We should screen for the sensitivity. We can take advantage of the test for the MDR mutation to assess for chemo sensitivity (see previous post and my e-book), before the chemo is started.
The second reason contributing to chemotherapy toxicity is because very little effort has been given, in particular in veterinary medicine, to actively decreasing side effects during chemo.
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In human medicine there have been some pharmaceutical advances, but very few veterinary oncologists are actively promoting things like coenzyme Q, carnitine, cordyceps, IP3, glutamine, or ginger during chemo.
I have am trying to make these more mainstream with this blog and The Dog Cancer Survival Guide, hoping that more veterinarians will promote decreasing chemotherapy toxicity.
Toxicity management is so important because we could use higher doses of our drugs (higher MTD’s) and improve our outcomes with less side effects.
In response to this need, a new facet has emerged from conventional medicine called metronomic chemotherapy.
Metronomic chemotherapy involves a very frequent, but low, dose of chemotherapy, especially with the use of the drug cyclophosphamide.
Metronomic chemo is different from traditional MTD chemo. In traditional chemo we use high doses for short periods, and the time off between treatments lets the body rebound.
In metronomic chemo, the lower doses lessen the toxicity risks.
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The guess behind the way metronomic chemo works is that it may prevent the new blood vessel cells that feed the tumor from working properly. The cells lining the blood vessels may be dying off.
Metronomic chemo is being looked at for use in children, and the veterinary community has recently started getting interested too.
Does it work? It is really too early to say, as even the human trial data is sparse. But there is some promise and it could be worth a try.
I think the best candidates would be for those dogs with low grade (but real), or slowly growing cancers that are difficult to cure with surgery.
If the cancers are growing too rapidly, the slower effects of metronomic chemo would not be practical.
This is another option that should be considered for dogs.
Best to all,
Dr. Demian Dressler is internationally recognized as “the dog cancer vet” because of his innovations in the field of dog cancer management, and the popularity of his blog here at Dog Cancer Blog. The owner of South Shore Veterinary Care, a full-service veterinary hospital in Maui, Hawaii, Dr. Dressler studied Animal Physiology and received a Bachelor of Science degree from the University of California at Davis before earning his Doctorate in Veterinary Medicine from Cornell University. After practicing at Killewald Animal Hospital in Amherst, New York, he returned to his home state, Hawaii, to practice at the East Honolulu Pet Hospital before heading home to Maui to open his own hospital. Dr. Dressler consults both dog lovers and veterinary professionals, and is sought after as a speaker on topics ranging from the links between lifestyle choices and disease, nutrition and cancer, and animal ethics. His television appearances include “Ask the Vet” segments on local news programs. He is the author of The Dog Cancer Survival Guide: Full Spectrum Treatments to Optimize Your Dog’s Life Quality and Longevity. He is a member of the American Veterinary Medical Association, the Hawaii Veterinary Medical Association, the American Association of Avian Veterinarians, the National Animal Supplement Council and CORE (Comparative Orthopedic Research Evaluation). He is also an advisory board member for Pacific Primate Sanctuary.