Animal Tales

by Dr. Howard A. Mintzer

Q. Mark F. of Wappingers Falls asks:

My 13 year old boxer, Brutus has just been diagnosed with a type of cancer called Lymphosarcoma. I'm going to have him treated with chemotherapy and hopefully he will recover. What I would like to know is how did he get cancer? Is it something I did? Should I have used a natural dog food with no added chemicals? Was it the chemicals in the flea and tick dips that I gave him? I'm really beside myself feeling that I am somehow to blame. What do you think?

A. Mark, I'd like to commend you on caring so much for Brutus that you're willing to go through the expense of treating his lymph node cancer. I think that you'll be pleased with the results. Lymph node cancer (similar to Hodgkin's disease in people) is one of the cancers that responds very well to chemotherapy. More importantly, dogs do not usually have the severe side effects (vomiting, lack of appetite, weakness, hair loss, etc.) that haunt people who undergo chemotherapy. Treatment may give Brutus a few more years to enjoy your company.

You are not to blame for Brutus' cancer. Over the past two decades we have been bombarded with news reports, articles, government warnings and the like that seem to infer that most cancers are caused by man made chemicals in the air we breathe and the food we eat. This is far from the truth. In an exhaustive scientific study in 1991 and in many articles after that, scientists Ames and Gold pointed out that 99.9% of the substances that cause cancer are natural substances that we eat and not "chemical additives" put into our food. Even the chemicals that the government warn us about have to be taken in enormous quantities to cause disease. The only cancer causing substance that people regularly take in quantities large enough to actually cause cancer is cigarette smoke.

If you really want to know how you "contributed" to Brutus' illness, I'll tell you what you did. You provided a good home, good food and good medical care so that Brutus could live to 13 years of age! That's right, you allowed him to get older than he ever would have without your love and care. The number one risk factor for cancer in humans and pets is AGE!

For one to understand cancer you need to refresh your understanding of biology. Each of our cells has genes which determine our characteristics. My brown eyes come from a gene that my mother and father passed on to me. Different genes are turned on and off by the body at different times in life. The gene that told the cells on my chin to start growing hair didn't get the signal to turn on until I was 13 years old. To my brother's great distress (but not for me!) the gene that told the cells on his head to grow hair somehow got the signal to turn off when he was 35.

Every day our cells reproduce. When a cell reproduces it copies its genes and pass the new copies on to its daughter cells. Occasionally during duplication, natural chemicals in the environment interfere with the copying process and mistakes are made. We call these mistakes mutations. The chances of a mutation happening are small, perhaps one in a million. Even with odds as low as one in a million, during a lifetime when millions of copies of the genes are made, some mutations are bound to occur. Most of the mistakes are inconsequential; perhaps the gene that limits the amount of pigment in the skin is damaged and you get a dark spot on your forearm. Sometimes though the results are more serious.

There is a special gene in every cell that controls the rate at which that cell grows and divides. The gene is very active before we are born and while we are developing, finally shutting down when we are fully grown. If that gene mutates it can cause the cell to start growing at a fantastic rate. This is how a cancer happens. One cell, with a mutated growth gene grows and grows until it takes over and destroys all the surrounding healthy body.

Realizing this, one can see that by far the main factor for the occurrence of cancer is age. The longer you live, the more times your cells reproduce and the more chance there is for genes to mutate. You might think that cancer is on the rise. That is not true. If we adjust for age the cancer rate among people in the United States for all cancers (except lung cancer) has either been steady or has decreased over the past 50 years. We do hear more about cancer. One reason is the media. Cancer is a scare word and any news article or TV show that mentions cancer will get people's attention. However, by far the main reason that there seems to be more cancer is that plain and simple, we are living longer.

The information we have on cancer in pets is more limited. But think about it. Under natural conditions Brutus wouldn't live to be 13 years old. Like his wolf fore bearers he'd be lucky to live past the ripe age of 5. Why do you think dogs are ready to have pups at a year of age? Reproduce early, raise your pups until they are old enough to have pups on their own and you've fulfilled your purpose in the scheme of things. By enabling Brutus to live to the very ancient age of 13 years you've increased his risk of getting cancer.

Instead of feeling guilty, be proud of how you've helped Brutus to live past his "natural" span and how you'll spend the rest of his time together. Good luck with his treatment,and feel assured that you've made the right decision.