Prostate Cancer

Prostate cancer is one of the most common cancers of older men, with a median age of onset of 72 years. It is the sixth most common cancer in the world and represents the third most common cause of cancer death in American men. However, because its age of onset is usually so late in life and because a variety of treatment options exist for both localized and advanced disease, many men with prostate cancer ultimately end up dying of other causes. In fact, many believe that if all men lived long enough, they would ultimately develop prostate cancer.

The prostate is a male reproductive gland located below the bladder that secretes the liquid components of semen. The prostate is composed mostly of glandular tissue and smooth muscle that contracts to help expel secretions. Prostate cancer is thought to exist along a spectrum of prostate diseases, which begins as a noncancerous enlargement of the prostate gland with age known as benign prostatic hypertrophy (BPH). In fact, age is the strongest risk factor for prostate cancer and prostate cancer onset is more closely correlated with age than any other cancer. Other risk factors for prostate cancer include race and ethnicity. African-American men have both a higher incidence [Page 1429]of prostate cancer and a younger age of onset overall. Genetics seem to play a role in the prostate cancer as well. Men with a first degree relative affected with prostate cancer are at higher risk of getting prostate cancer and this risk increases with the number of affected first-degree relatives. Other risk factors include diet. Research suggests that a diet high in animal fat and low in vegetables, vitamin E, and the metal selenium may predispose men to prostate cancer. There is also evidence to suggest that zinc supplements may increase risk, while the anticholesterol drugs known as statins may decrease risk. Finally, because the prostate gland is a reproductive gland whose growth is dependent on certain male hormones, it has been suggested that men with higher levels of testosterone and insulin-like growth factor are more likely to develop prostate cancer.

The presentation of patients with prostate cancer varies widely. Because of the prostate's proximity to the bladder, some prostate cancers can cause enlargement of the prostate gland and impingement on the portion of the urethra that penetrates the prostate. These patients typically experience difficulty initiating urination, urinary tract infections and/or hematuria, or blood with urination. Because prostate cancer can develop in parts of the gland that do not affect the urethra, many patients can be asymptomatic. However, even silent presentations of prostate cancer can be detected through annual digital rectal exams and prostate-specific antigen (PSA) screening. PSA is a protein that the prostate secretes during periods of inflammation, but it is also elevated in the setting of BPH or prostate cancer. Although elevations in PSA can be very useful in screening for prostate cancer or in suggesting a recurrence, the test is not entirely sensitive or specific. This means that a minority of patients with cancer will not have elevated PSA and that elevations in PSA may not necessarily indicate that a patient has cancer. Some patients may present in advanced stages of prostate cancer where the cancer has spread to distant sites. Because frequent sites of metastasis include the bone and brain, these patients may present with back pain and difficulties walking from metastasis to the vertebrae.

...