Don’t Feel Guilty: Sometimes Cancer Really Is Just Bad Luck

Cat being examined by a veterinarian
Cat and dog owners no longer have to feel guilty when their pets are diagnosed with cancer. According to a recent article in the journal Science, sometimes cancer is just bad luck.

As a veterinary cancer specialist, I talk to distraught pet owners every day who are in shock and grief over cancer diagnoses for their beloved pets. They are looking for answers. What does this diagnosis mean? When did the tumor start? How long will my pet live? How will the treatment make my pet feel? But the million dollar question is “Why does my pet have this tumor?”

Most of the time, I have no idea why a dog or cat develops a particular tumor. Occasionally, I see a cat infected with feline leukemia virus — a known cause of feline lymphoma. We also know genetics play a role in whether some pets get cancer, because some tumors run in breeds. For example, Pugs are prone to mast cell tumors and hemangiosarcomas are common in Golden Retrievers. Reproductive status matters as well. Female dogs who are not spayed before their first heat (or those not spayed at all) have a much higher rate of breast cancer. Body size also plays a role in the development of bone cancer, since the typical dog with this disease weighs more than 70 pounds. But these examples describe only a few of my patients.

The Answer to a Vexing Question

Because I don’t know why most of my patients get cancer, and out of desperation to answer this question for owners, I started telling them, “It’s just bad luck.” Well, it turns out I may have been right.

A recent article in the prestigious journal Science and reported on by The New York Times blames cancer on random mutations arising during DNA replication.

The research behind the article, authored by two scientists at Johns Hopkins University in Baltimore, started with the observation that certain body parts develop cancer at different rates. For example, the colon develops cancer more commonly than the esophagus, even though these structures are both part of the same digestive “tube” in your body. Using seriously high-powered math, they determined most cancers develop because of a random process.


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