Regular exercise helps reduce stress, another lifestyle factor in the development of cancer. Uncontrolled stress has been shown to exacerbate tumor growth in humans. Signs of stress in your dog vary from obvious (digestive upset or lack of appetite) to subtle (persistent licking with no other cause, yawning, scratching for no obvious reason, dropped tail, drooling, low/back ears). Feed a good-quality food in appropriate amounts to keep your dog fit and slender. Be sure your dog gets plenty of exercise, and address stress issues by incorporating the help of a trainer or your veterinarian to isolate and eliminate the source.