By Dr. Becker
According to the National Cancer Institute (NCI), the top five cancers in people are breast cancer in women, prostate cancer in men, followed by lung cancer, colon/rectal cancer, and melanoma in both sexes.1
When it comes to our pets, there's no national organization that tracks the occurrence of cancer. We do know that many common human cancers are not prevalent in pets, but there are other cancers we do acquire in common, including breast (mammary gland) cancer, lymphoma, skin cancer that takes the form of mast cell tumors in pets, and bone cancer.
Four Common Types of Pet Cancer
Mammary gland cancer. Mammary gland or breast cancer is common in both dogs and cats. It is the most common tumor found in female dogs and the third most common in cats.
One of the presumed and much-touted benefits of early spaying of female pets is a decreased risk of mammary gland cancer. However, a study published in 2012 in the Journal of Small Animal Practice found that insufficient evidence exists that spaying at any age reduces the risk of mammary cancer.2
Lymphoma. Lymphoma is an incurable cancer of the lymph system, which is part of the immune system. In cats, one in three cancer diagnoses is lymphoma, most often of the GI tract. Dogs also develop lymphoma.
To avoid contributing to your dog's or cat's lymphoma risk, make sure your pet isn't exposed to cigarette smoke or lawn pesticides, especially those applied by professional lawn care companies.
Mast cell tumors. The most common type of skin cancer in pets is mast cell tumor (MCT). MCT is much more prevalent in dogs than in cats. In cats, mast cell tumors are most often seen in the skin of the head or neck, but they can occur anywhere in the body. Cats with these tumors are usually middle-age or older. Unfortunately, kitties with mast cell tumors on the inside of their bodies -- typically in the GI tract or the spleen -- carry a much poorer prognosis than tumors occurring on the skin.
In dogs, mast cell tumors are most often found on the trunk, limbs, and in between the toes. Prognosis depends on the tumor location, the extent of the tumor, the grade, and the type of treatment given. Mast cell tumors of the skin are very different in dogs than cats. Surgery to remove the tumor is less invasive in cats, and the prognosis for a full recovery is much better in cats than in dogs.
Mast cell tumors with generally poor prognosis are those on the muscle, around the mouth or in internal organs, in the bloodstream or bone marrow, and ulcerated tumors. Mast cell tumors that cause GI ulceration or are large, fast-growing, or recurring also carry a much poorer prognosis.
Bone cancer (osteosarcoma). Osteosarcoma is a common and aggressive bone cancer that invades the long bones of large and giant breed dogs. Even with amputation of the affected limb and chemotherapy, which is the current standard of treatment, the average survival rate is only about a year.
10 Warning Signs of Cancer in Pets
According to the Colorado State University Flint Animal Cancer Center, the top 10 warning signs of cancer in pets are:3
- Unusual swellings that don't go away or that grow. The best way to discover lumps, bumps, or swelling on your dog or cat is to pet him.
- Sores that won't heal. Non-healing sores can be a sign of infection or cancer and should be evaluated by your veterinarian.
- Weight loss. Illness could be the reason your pet is losing weight but isn't on a diet.
- Loss of appetite. Reluctance or refusal to eat is another sign of possible illness.
- Bleeding or discharge. Bleeding can occur for a number of reasons, most of which signal a problem. Unexplained vomiting and diarrhea are considered abnormal discharges, as well.
- Offensive smell. An unpleasant odor is a common sign of tumors of the anus, mouth, or nose.
- Difficulty eating or swallowing. This is a common sign of cancers of the mouth or neck.
- Reluctance to exercise or low energy level. This is often one of the first signs that a pet is not feeling well.
- Persistent lameness. There can be many causes of lameness, including nerve, muscle, or bone cancer.
- Difficulty breathing, urinating, or defecating. These symptoms should be evaluated by your veterinarian as soon as possible.
Tips for Reducing Your Pet's Cancer Risk
• Don't allow your pet to become overweight. Studies show that restricting the amount of calories an animal eats prevents and/or delays the progression of tumor development across species.
Fewer calories cause the cells of the body to block tumor growth, whereas too many calories can lead to obesity, and obesity is closely linked to increased cancer risk in humans. There is a connection between too much glucose, increased insulin sensitivity, inflammation, and oxidative stress – all factors in obesity – and cancer.
It's important to remember that fat doesn't just sit on your pet's body harmlessly. It produces inflammation that can promote tumor development.
• Feed an anti-inflammatory diet. Anything that creates or promotes inflammation in the body increases the risk for cancer. Current research suggests cancer is actually a chronic inflammatory disease. The inflammatory process creates an environment in which abnormal cells proliferate.
Cancer cells require the glucose in carbohydrates to grow and multiply, so you want to limit or eliminate that cancer energy source. Carbs to remove from your pet's diet include processed grains, fruits with fructose, and starchy vegetables like potatoes. Keep in mind that all dry pet food contains some form of starch. It may be grain-free, but it can't be starch-free because it's not possible to manufacture kibble without using some type of starch.
Cancer cells generally can't use dietary fats for energy, so appropriate amounts of good-quality fats are nutritionally healthy.
Another major contributor to inflammatory conditions is a diet too high in omega-6 fatty acids and too low in omega-3s. Omega-6s increase inflammation while the omega-3s do the reverse. Processed pet food is typically loaded with omega-6 fatty acids and deficient in omega-3s.
A healthy diet for your pet – one that is anti-inflammatory and anti-cancer – consists of real, whole foods, preferably raw. It should be high in high-quality protein, including muscle meat, organs, and bone. It should include moderate amounts of animal fat and high levels of EPA and DHA (omega-3 fatty acids, such as krill oil), a few fresh cut veggies and a bit of fruit.
This species-appropriate diet is high in moisture content and contains no grains or starches. I also recommend adding a vitamin/mineral supplement and a few beneficial supplements like probiotics, digestive enzymes, and super green foods.
• Reduce or eliminate your pet's exposure to toxins. These include chemical pesticides like flea and tick preventives, lawn chemicals (weed killers, herbicides, etc.), tobacco smoke, flame retardants, and household cleaners (detergents, soaps, cleansers, dryer sheets, and room deodorizers).
Because we live in a toxic world and avoiding all chemical exposure is nearly impossible, offer a periodic detoxification protocol to your pets.
• Allow your dog to remain intact (not neutered or spayed), at least until the age of 18 months to two years. Studies have linked spaying and neutering to increasing cancer rates in dogs. A 2002 study established an increased risk of osteosarcoma in both male and female Rottweilers neutered or spayed before the age of one year. Another study showed the risk of bone cancer in neutered or spayed large purebred dogs was twice that of intact dogs.
• Refuse unnecessary vaccinations. Vaccine protocols should be tailored to minimize risk and maximize protection, taking into account the species, breed, background, nutritional status, and overall vitality of your pet.