Prostate Cancer

Prostate cancer is very uncommon in dogs, found in only 0.67% of dogs over 8 years old. The most common signs of prostate cancer are weight loss, difficulties in defecating and urinating, and weakness in the hind leg.

Most canine prostate cancers are adenocarcinomas derived from glandular tissue. Prostate cancers may rarely be associated with hormones produced by the testicles, adrenal glands, or pituitary glands. Unlike human prostate cancer, which is often indolent and slowly growing, canine prostate cancer is an aggressive and invasive disease that metastasizes rapidly to the lymph nodes, lungs, and bone. Dogs are usually diagnosed in the late stages of the disease, often when the tumor has spread to the lumbar spine and brain. The prognosis of late stage canine prostate cancer is poor.

Prostate cancer is best diagnosed initially with contrast radiography. A cytology study of a urine sample may help to confirm the diagnosis, although a biopsy of the rectal wall is normally used for a definitive diagnosis.

Standard Treatment

Canine prostate cancers that are hormone responsive may be successfully treated with castration. However, most prostate tumors are not hormone-responsive, and the prognosis in these cases is poor. Because the structure of the canine prostate is much more complex than in humans, surgical resection of even very early cases of prostate cancer can be extremely hazardous to the patient. The general survival time for dogs with prostate cancer is approximately 6 weeks after diagnosis.

Antiangiogenic therapy may be a possible treatment for canine prostate cancer. Researchers in Boston have found that dogs with prostate cancer normally produce angiostatin, a natural angiogenesis inhibitor, which is present in their bloodstream. This discovery suggests that angiostatin therapy may be one antiangiogenic strategy to treat this disease. In human patients, a number of angiogenesis inhibitors have entered clinical trials for prostate cancer, including Avicine, CT-2584, flavopiridol, LDI-200, Neovastat, thalidomide, suramin, and TNP-470.