The prostate, located between the bladder and the rectum, secretes seminal fluid, in which the sperm are carried. It also tends to enlarge as a man grows older, sometimes obstructing urinary flow and increasing both the frequency and difficulty of urination. This condition, known as benign prostatic hypertrophy (BPH), is not cancer, and the surgical treatment sometimes used for it is different from the treatment for prostate cancer.
An estimated 25 million American men over 50 have prostate cancer, though that doesn't mean all of them have symptoms of the disease or will die of it. The lifetime risk of getting prostate cancer is about one in 10). But only about 25% of those who get prostate cancer die of it. Only 3% of all men die of prostate cancer.
The blood test measures levels of a protein known as prostate specific antigen, or PSA, which may be elevated when prostate cancer is present. The digital rectal exam, or DRE, in which a doctor inserts a gloved finger into the rectum and examines the lower part of the prostate gland for any abnormality, is another way to screen for prostate cancer, and though it misses more cancers than PSA, it is by no means outmoded. The PSA as a screening test for prostate cancer is endorsed by such groups as the American Cancer Society, the American Urological Association, and other medical groups.
If you're a man approaching 50, it's important to think about the issues before you get the test. Here are some questions you should ask your doctor first:
Of 100 men over age 50 getting a PSA, 10 to 15 will be found to have an elevated level. However, only about 3 or 4 will actually have cancer. The rest are false-positive tests. These men, however, will most likely have to undergo a prostate biopsy to be assured that they don't have cancer. This ends up putting a lot of men through unnecessary, uncomfortable and anxiety-provoking testing, all for nothing. And there are false-negatives, too - cancers that go undetected because they don't cause an elevated PSA, about one-quarter of all prostate cancers. So a negative result should not be taken as absolute reassurance.
If prostate cancer is detected, there's no standard recommendation for treatment. Younger men (under 60) are more likely to benefit from aggressive treatment if they have an aggressive cancer. Some men may feel that once diagnosed with cancer they must proceed with surgery. (They should try to find an experienced surgeon who knows how reduce the risk of such complications as impotence and incontinence.) Older men may decide on external radiation or brachytherapy (implantation of radioactive "seeds"). Others may opt to watch and wait. But discuss all options with your physician, and learn all you can. A second opinion is essential.
The CDC has a nice site going over this information as well. We have a version of this website in a pdf file at your fingertips as well as a nice discusion from the Darmouth Center for Shared Decision Making.