Tuesday, August 16, 2022

My son Eitan recently acquired a new dog, Sparky. Eitan and my wife Elie love Sparky, and Sparky seems to love them. Enough said. I do have to say he is adorable. And he does remind me of the following story:

One afternoon in late 2000, I was sitting in my office when I received a phone call from a woman who introduced herself as an oncologist. She explained that she had a patient with advanced breast cancer and wanted information on the use of tamoxifen, an anti-estrogenic hormone widely utilized in that setting. I did not know how she came to me, and it struck me as odd that an oncologist was unfamiliar with this standard drug, but we discussed it for a while.

It turned out that the woman (I forget her name) was a veterinary oncologist. Indeed, she was the chief of oncology at the Animal Medical Center, the large veterinary hospital located at East 62nd Street opposite the FDR Drive, and which I often confused, as I was driving, with NYU Medical Center. She subspecialized in dogs, and had a new patient with metastatic breast cancer and wanted to try tamoxifen. As it evolved, she did try the drug with great success.

We ended up having a couple of great discussions regarding veterinary cancer, a fascinating subject, and human cancer, also interesting, and she invited me to a regional Veterinary Cancer Society conference that took place a few months later, at which I gave the keynote address on human cancer epidemiology. It turns out that the veterinary oncologists had great interest in humans.

The conference, which was held at the Animal Medical Center, gave me the opportunity to tour the facility, and I also learned a lot about cancer in dogs, some of which I recount here.

Lung cancer is, under normal circumstances, a very uncommon malignancy in dogs. When it does occur, it is almost invariably in a dog that is owned by someone who is a heavy smoker. There are several case-control studies of lung cancer in dogs that have confirmed this quite conclusively. Until learning this, I have to confess that I was personally quite skeptical regarding the evidence in support of second-hand smoke as a factor in lung cancer causation—most of its victims were themselves former smokers in the studies. But these studies of canine lung cancer were indisputable. Furthermore, the length of the dog’s snout also played a role in lung cancer causation. Apparently the longer the snout, the lower the risk—a long snout protected against the inhalation of the tobacco carcinogens. I later looked for but could not find a similar study of nose size in humans and risk of lung cancer.

As a corollary to the above, nasal cancer is also common in dogs. Again, environmental tobacco smoke doubles the risk to the dog. The anatomy of the skull and nose also plays a role.

Breast cancer in humans is hormone-receptor positive in about two-thirds of cases. In dogs, it is virtually always hormone-receptor positive. Thus, the use of hormonal therapy, like tamoxifen, was a highly effective approach to affected dogs.

Interestingly, dogs are the only known species, aside from humans, in whom prostate cancer occurs. It is not common, but dogs can undergo total prostatectomies as is done in humans. Another cancer that is common in dogs is osteogenic sarcoma. As in humans, if the owner wishes to be aggressive, amputation and chemotherapy can be utilized and can be effective.

When I toured the Animal Medical Center, I also saw some unfortunate dogs receiving chemotherapy. When I inquired, I learned that these were dogs with lymphoma. Similar to humans with non-Hodgkin lymphoma, there are at least 30 forms of lymphoma that fall under the rubric of lymphoma and that vary in aggressiveness; there does not seem to be Hodgkin lymphoma to any significant degree in dogs.

When I asked my host how she was treating the dogs with lymphoma, she responded, “With CHOP.” CHOP is a four-drug regimen that is commonly used for non-Hodgkin lymphoma and is quite effective. I responded, “CHOP? That is what we use for our patients!” To which she replied with a smile, “We try not to give anything to our patients until it has been proved safe and effective in humans.”

Alfred I. Neugut, MD, PhD, is a medical oncologist and cancer epidemiologist at Columbia University Irving Medical Center/New York Presbyterian and Mailman School of Public Health in New York.

This article is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment, and does not constitute medical or other professional advice. Always seek the advice of your qualified health provider with any questions you may have regarding a medical condition or treatment.

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