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Ask a Vet: Can Cannabis Treat Breast Cancer in Cats?

Cannabis has numerous potential uses, but it's becoming the modern-day snake oil.

Dr. Eric Barchas  |  Feb 16th 2016


I recently received a query from a pet owner.

My older lady cat has very swollen and hard breast tissue on her lower breasts. We have been recommended treatment of cannabis oil orally and directly, mixed with olive oil. Is this the correct way to go? If so how much should we use and how long should it take?

Every time I read that question I am compelled to sigh. Where should I begin? Let’s start with breast cancer in cats.

Breast cancer is not uncommon in cats who have gone through several heat cycles, especially if they have not borne litters. It appears that the hormonally triggered patterns of mammary growth and diminishment that accompany heat cycles can, in some circumstances, trigger uncontrolled growth of breast tissue. Totally uncontrolled growth of tissue has a name: cancer.

Photo of Dr. Eric Barchas by Liz Acosta

Photo of Dr. Eric Barchas by Liz Acosta

Mammary tumors come in two broad categories. There are benign tumors, which tend to grow in one spot but do not spread to other organs and rarely threaten life. Malignant tumors, on the other hand, might spread throughout local tissue and might also spread to distant sites in the body.

In cats, most breast tumors are malignant. The majority of mammary (breast) masses in cats consist of a type of cancer called mammary adenocarcinoma. The cat mentioned in the query I received probably has mammary adenocarcinoma. In other words, she probably has breast cancer.

Mammary adenocarcinoma starts as a hard lump or several hard lumps in one or more breasts. The tumors might spread to other breasts, the tissues around the breasts, and to lymph nodes near the breast. The tumors might become large, causing ulcers and infections. They might spread to the lungs or other vital organs, with life-threatening consequences.

Sound familiar? Breast cancer in cats is in many way similar to breast cancer in people.

Consider this: For many years there have been campaigns to raise awareness of breast cancer in people. I daresay those campaigns have been very successful. Pink ribbons are quite ubiquitous in our society. Breast cancer is on peoples’ minds, and everyone is hoping for a cure.

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Cannabis by Shutterstock

Marijuana, as it turns out, also is pretty ubiquitous in our society — especially in places where it is legal for medical or recreational use. Don’t you think, with all of the people consuming cannabis, all of the people who want to promote the legal use of cannabis, and all of the people who want to cure breast cancer, that someone would have noticed if cannabis could cure or treat breast cancer? It would be simple to run an epidemiological study that would, after adjusting for confounding variables, reveal lower rates of breast cancer among cannabis users. Such a study would be downright earth-shattering. It would garner huge front page headlines on newspapers everywhere. US (and world) drug policy would change overnight.

I strongly suspect I know why news of cannabis as a breast cancer treatment never has made the headlines. Cannabis does not treat breast cancer.

The query from the cat owner bothers me on many levels. Where did this person get his information? Who is recommending cannabis instead of something that might help? I’m guessing the answer is a huckster.

The cat in question desperately needs veterinary attention. Instead the owner is mucking around, asking Internet vets about modern day snake oils.

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A kitten and mother cat by Shutterstock

That’s right: Cannabis is turning into the snake oil of the modern era. People are claiming that cannabis can do all sorts of things that it simply cannot. Animals are suffering as a consequence.

I have another issue with this matter. Ridiculous and fraudulent claims about cannabis impair research into legitimate uses for the product. In humans cannabis has demonstrated potential to treat pain, insomnia, inappetence from chemotherapy, anxiety disorders, and other ills. It is highly probable that formulas and molecular structures can be tweaked to help cats with these problems as well.

But people who make ridiculous claims about cannabis demean the credibility of the product in general. With so many hucksters promoting cannabis for outlandish and outrageous purposes, people might turn against the research that would help uncover legitimate uses and formulations that might help animals and people.

What would motivate people to make outlandish claims about cannabis’ medical uses? I’m guessing it’s the same thing that has motivated snake oil salesmen since time immemorial: profit. There’s money to be made by selling THC oil to unsuspecting suckers. But that profit comes at a price to the animals who are denied proper treatments, and to the animals who might benefit from legitimate uses of cannabis.

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