Dog: Prostate Cancer

General information

The prostate is considered an accessory sex gland. It is a bi-lobed structure that lies just behind the bladder and under the colon, surrounding the urethra (the tube which carries urine from the bladder). The prostate produces fluid which both nourishes and gives volume to the sperm. This fluid enters the urethra as it courses through the prostate gland. Sperm cells from the testicles mix with the prostatic fluid in the urethra. The urethra then carries the semen through the penis during ejaculation.

The prostate gland starts to develop before the male dog reaches puberty. Testosterone, produced in the testicles, is responsible for the growth of the prostate. It attains its maximum size by about two years of age. Due to the lack of testicles and thus testosterone, dogs that are castrated before puberty have very small prostate glands.

Fortunately, prostate cancer is uncommon in dogs. However, when it does occur, it is usually malignant, spreading through the body to the lymph nodes, liver, lungs, bone or kidneys. It is usually seen in older dogs (10 years or older). Intact (non-castrated) and castrated male dogs are equally affected by prostatic cancer.

Cardinal symptom

Enlarged prostate


An enlarged prostate may cause signs of straining and pain to urinate and defecate. Bloody urine may be present. In cases where the cancer has spread, weight loss, lack of appetite and lethargy are present. Advanced cases involving metastasis (spread of cancer) to the bone may show signs of back pain and pelvic weakness are noted.


All mature dogs should have a prostatic examination annually. This is performed by your veterinarian inserting a gloved finger in the rectum and palpating (feeling) the prostate. A castrated male should have a small prostate. If enlarged, prostate cancer is most likely. Dogs that are not castrated may have enlarged prostates from benign hyperplasia or prostatitis (see article on prostate enlargement). In these cases, a urinalysis should be performed to look for cancerous cells. Radiographs and ultrasonography of the prostate, abdomen and chest will aid in diagnosis and check for spread of the disease. A fine needle aspirate or biopsy can be used to confirm the diagnosis.


There is no cure for prostate cancer in dogs. Treatment is usually aimed at providing comfort and reducing pain with medication for the remainder of the dog’s life. Other treatment are available if the cancer has not spread. These treatments, which are expensive and only available at referral hospitals or universities, include:

  • Radiation: can help shrink the tumor and alleviate clinical signs.
  • Chemotherapy: can be used in combination with radiation to decrease tumor size and reduce inflammation.
  • Prostatectomy: surgical removal of the prostate. This is a very difficult surgery to perform and is usually not recommended.


Because there is no cure for prostate cancer, the prognosis is poor. In most cases, the cancer has already spread to other organs by the time it is diagnosed. Most dogs die within months of diagnosis.


There is no prevention of prostate cancer.

Update version: 4/24/2014, © Copyright by
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