Excerpt from:  http://healthypets.mercola.com/sites/healthypets/archive/2014/01/15/canine-osteosarcoma.aspx

5 Ways to Reduce Your Dog's Cancer Risk

Don't allow your dog to become overweight. Studies prove that restricting the amount of calories an animal eats prevents and/or delays the progression of tumor development across species, including canines.

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 for dogs.

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), 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 dog'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, 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.1 Another study showed the risk of bone cancer in neutered or spayed large purebred dogs was twice that of intact dogs.2

Refuse unnecessary vaccinations. Vaccine protocols should be tailored to minimize risk and maximize protection, taking into account the breed, background, nutritional status and overall vitality of the dog. The protocol I follow with healthy puppies is to provide a single parvo and distemper vaccine at or before 12 weeks, and a second set after 14 weeks. I then titer (ask your vet to run titers at a lab that uses the IFA method) two weeks after the last set and if the dog has been successfully immunized, he is protected for life.

If titer tests indicate vaccine levels are low (which would be incredibly unlikely), I recommend a booster for only the specific virus or viruses that titered low, and only for those to which the animal has a real risk of exposure. I do not use or recommend combination vaccines (six to eight viruses in one injection), which is the standard yearly booster at many veterinary practices.