Melanomas – prevention and treatment

About 4% of skin tumors are melanomas, and they are one of the most common tumors in the canine mouth. They arise from pigment cells, so they are usually black and occur more often in dogs with black skin. In addition, miniature and standard Schnauzers, are more likely to get melanomas of the skin. Small dogs with dark gums, chows, golden retrievers, Scottish terriers, and peke-a-poos are more likely to get melanomas of the mouth. In dogs, most melanomas of the skin are benign, but most melanomas of the mouth or at the base of their nails, are malignant. Malignant tumors can spread to other parts of the body, eventually causing death.

Unlike people, there is no good evidence that exposure to the sun causes melanomas in dogs or cats. But one other factor that owners can control does play a part: obesity. Most veterinarians define obesity in dogs and cats as weighing 20% more than their ideal weight. (Is your pet overweight? Recommended weight ranges for body types of cats, and the top 100 breeds of dogs can be found at http://www.petobesityprevention.org/ideal-weight-ranges/). According to the Association for Pet Obesity Prevention (www.petobesityprevention.org), about 58% of cats and 54% of dogs in the U.S. are overweight, with 17.6% of dogs, and 28.1% of cats weighing 30% more than their ideal bodyweight. This number has been increasing each year. (In 2013 16.7% of dogs and 27.4% of cats were in this category.)

But many people don’t know when their own dog or cat is overweight. Dr. Steve Budsberg, veterinary orthopedic specialist and Director of Clinical Research for the College of Veterinary Medicine at the University of Georgia, says. “Whenever (an owner’s) veterinarian tells them their pet needs to lose weight, they often can’t believe it because they don’t see it.”

You can get a visual idea of whether or not your pet has a problem by comparing their outline to charts of body scores, such as the ones at http://vet.osu.edu/vmc/companion/our-services/nutrition-support-service/body-condition-muscle-condition-score-charts

Royal Canin does this a different way: they have a chart with a slider which you can move to make the picture match up with your pet. See http://www.royalcanin.co.uk/knowledge-centre/body-condition-score/

Fat produces some cancer-promoting chemicals, and fat also produces chemicals that speed up growth and metastasis of cancer. Reducing calories in obese people with melanoma shrank the tumors. They found that it decreased the production of new blood vessels to cancer and increased the amount of dead cancer tissue. Some chemical factors that contribute to the growth of melanomas were decreased when calories in the diet were decreased. Also, a high fat diet, which some people who are making their own pet food can accidentally create, increased the spread of melanomas to nearby lymph nodes.

Besides putting your overweight pet on a diet, there are some nutritional supplements that have been shown to decrease the tendency of melanoma to invade normal tissues, and to metastasize to other parts of the body. Research has shown these actions for grape seed extract, EGCG (from green tea), curcumin, silymarin (from milk thistle) and berberine.

Further reading – the research

Jane M. Dobson JM, Breed-Predispositions to Cancer in Pedigree Dogs, ISRN Vet Sci. 2013; 2013: 941275. Jones V, Katiyar S, Emerging phytochemicals for prevention of melanoma invasion. Cancer Lett. 2013 July 28; 335(2): 251–258.

Jung JI, et al, High-fat diet-induced obesity increases lymphangiogenesis and lymph node metastasis in the B16F10 melanoma allograft model: roles of adipocytes and M2-macrophages. Int J Cancer. 2015 Jan 15;136(2):258-70.

Malvi P et al, Malvi P et al, Obesity induced rapid melanoma progression is reversed by orlistat treatment and dietary intervention: role of adipokines. Mol Oncol. 2015 Mar;9(3):689-703.

Sergentanis TN, et al, Obesity and risk of malignant melanoma: a meta-analysis of cohort and case-control studies. Eur J Cancer. 2013 Feb;49(3):642-57.