The Dog Cancer Survival Guide (28 page)

Pesticides and herbicides used in home and lawn care can be a source of airborne carcinogens. The use of 2,4-D, an herbicide found in over 1,500 weed-killers, was found to increase lymphoma rates (the study was later refuted, but even mixed evidence concerns me). Lawn pesticides have also been found to be associated with transitional cell carcinoma, the most common type of bladder cancer.

Researchers do not fully understand how high voltage power lines create airborne carcinogens, but an increased incidence of cancer (particularly childhood leukemia) is associated with them, and slightly more so downwind. The cause could be magnetic fields or their generation of a carcinogenic particle (called a corona ion) in the air around the lines, or other factors. This is another area of research where initial evidence was later disputed and yet is once again a topic of interest. Despite the mixed response of the medical community, you as a guardian will want to be aware of the higher incidence of cancer associated with high voltage power lines.

If you take the air we breathe for granted, this information may feel a little overwhelming. As most of these airborne carcinogens are invisible, how can you be certain you’re avoiding them? It’s not possible, or desirable, to put your dog in a bubble, but it is worth thinking about ways to keep her air as clean as possible.

For example, keep your dog away from areas (inside or outside) that have been treated with pesticides or herbicides, for at least six hours after application. If you smoke, consider making her area a smoke-free zone. If your house needs a new coat of paint, wait to do the interior walls, or remove your dog from the home while you do. The same goes for the use of solvents. If your dog spends a lot of time in or near the garage, consider moving her away from the area to reduce her exposure to car exhaust. Try to avoid walking your dog on busy streets. The same advice applies if you use kerosene in heaters, stoves, or lamps, and also coal heaters. Be sure to ventilate well, when using these appliances.

Industrial manufacturing processes usually produce by-products, and this waste does not always go up in smoke. Sometimes it goes into the ground, where it can stay for years, spreading carcinogens into the soil, and even the water table that feeds wells and reservoirs.

We didn’t always understand just how hazardous industrial waste is to our health. Entire communities have been built on top of landfills, packed with industrial waste. One of the most famous of these is a neighborhood in Niagara Falls, New York, named Love Canal. Twenty-one thousand tons of chemical waste, buried in drums, started leaking and caused a public health emergency and a national scandal in the late 1970’s. The Environmental Protection Agency (EPA) classifies sites like Love Canal as National Priority Sites – also known as “Superfund sites.” As of this writing, there are 1,279 such sites in the U.S.! Obviously, human health problems are higher in locations contaminated with toxic waste. I haven’t seen a study specifically looking at cancer rates in dogs living near Superfund sites, but I would guess that their health likely suffers as well.

To find out if you are close to a Superfund site, go to the EPA’s website:
www.epa.gov/superfund/sites.

Inflammation is a natural response to bodily injury. If you are stung by a bee, have acid indigestion, or suffer a cut, inflammation brings extra blood and lymph to the injury. These fluids make the tissue warm, red, and swollen with cells that help fight infection and repair the injury.

In acute situations like these, inflammation is an immediate and helpful response; much like the fire department’s showing up when your house is on fire: you may be relieved and thankful they can put it out, but if they are still spraying water after it is extinguished, they would be causing damage to your home, not preventing it.

The same is true of inflammation. If inflammation lasts for too long, or if it becomes a chronic, low-level (often undetectable) condition, inflammation can wreak some pretty serious damage.

As we’ve already discussed in
Chapter 6
, inflammation can help cancer to metastasize by destabilizing DNA, helping the tumor build new blood vessels, and even by stimulating tumor growth. My own clinical experience agrees with this; when I examine a cancer patient’s history, I often find factors that could have led to microscopic levels of long-term inflammation. For example, diets with high levels of omega-6 fatty acids and not enough vegetables are common. Obesity is another common culprit; obesity is related to low-grade body inflammation in humans, and has been shown to pose a cancer risk for dogs.

You’ll read more about overfeeding, omega-6 fatty acids, and the importance of vegetables in
Chapter 14
. The dog cancer diet can help reduce the possible presence of chronic, microscopic inflammation in your dog.

Certain dogs have been bred over many hundreds, and in some cases, thousands of years. Human intervention has strengthened certain traits, including intelligence in herding dogs, acute smell in hounds, and cooperation in sporting dogs. Sometimes less visible traits have been passed down as well, including DNA encoded for cancer development. This is why some breeds are more prone to cancer overall and why certain breeds are more prone to certain cancers.

For example, if two individual dogs with the same cancer-causing mutated gene are mated, their pups may have a much higher probability of developing cancer than the parents.

There are also entire breeds with a very high probability of developing cancer. Both Boxers and Golden Retrievers have exceptionally high cancer rates, and 75% of Goldens
die
of cancer.

Responsible breeders can help improve bloodlines by avoiding breeding dogs whose parents or grandparents developed cancer. If a tendency to develop cancer is in the historical breed line, it will always be a potential hazard in descendants. This is probably why mixed breed dogs have much lower cancer rates than purebred dogs.

*Note: This lists some common examples of breed-related cancers, but it is not comprehensive

Mammary cancer is the second most common form of dog cancer, and it can be nearly completely eliminated by spaying a female dog before the first heat, probably because removing the ovaries and uterus reduces the production of sex hormones and keeps breast tissue from developing. On average, the first heat arrives at six months of age and recurs approximately every six months until late in life.

Spaying provides less protection with every passing heat. Studies have shown that dogs spayed before the first heat have a 0.05% risk of developing mammary cancer, when compared to intact female dogs, which means the risk is almost completely eliminated by the surgery. If the spay happens between the first and second heats, female dogs still have quite a bit of protection, with only an 8% risk, compared to their intact sisters. If the spay happens between the third and fourth heat, female dogs have a 26% risk, compared to intact dogs (and some oncologists cite a paper that puts this risk at a much lower 6%). Clearly, spaying a female dog reduces her risk of mammary cancer. It also removes all risk for ovarian and uterine cancer.

For a male dog, neutering (removing the testicles) decreases the risk of benign perianal adenomas and also eliminates his risk for testicular cancer.

If you just look at these factors, spaying and neutering might seem like an obvious choice. It’s not. There is actually evidence that spaying and neutering increases the risk for other aggressive cancers.

The following data may create a negative reaction among some (maybe even most) practicing veterinarians. This information has not been widely publicized in veterinary circles, even though it is from published, peer-reviewed papers with respected authors. It represents a very inconvenient truth for us vets. How will we reconcile population control and the euthanasia of unwanted pets with the associations between spaying, neutering, and cancer development? These are murky ethical waters for animal lovers. (The scientific references for this are located in
Appendix E
.)