Since the introduction of a blood test to screen for prostate cancer in 1986, more than 1 million additional U.S. men have been diagnosed and treated for prostate cancer, a U.S. team reported on Monday, raising fresh questions about high rates of over-diagnosis.
Here are some facts about prostate cancer treatment, and the prostate-specific antigen or PSA screening test:
* Prostate-specific antigen PSA screening is a test that looks for elevated levels of a protein produced only by cells in the prostate gland. Prostate tumors can elevate PSA but so can a condition called benign prostatic hyperplasia -- an enlargement of the prostate that comes with age.
* Most men who develop prostate cancer do not suffer any serious consequences related to the cancer and die of some other cause. PSA tests cannot distinguish between aggressive and low-risk cancers.
* Prostate cancer treatments, including surgery or radiation, can cause incontinence and erectile dysfunction in about a third of patients. Many men also experience bowel problems.
* PSA tests cost $70 and up.
* Many researchers are working on better diagnostic tests that look for aggressive forms of cancer, including molecular changes that suggest the cancer may spread.
* Some have studied PSA velocity, the change in PSA levels over time. A sharp rise may signal aggressive cancer, but more studies are needed. Other teams are examining PSA density, which looks at PSA levels in relation to the size of the prostate gland.
* Other potential tests: Some teams have found that the pattern of small bits of genetic material called microRNAs in a cell differ between normal and abnormal cells, raising hope for a new way to identify potentially harmful cells.
* Genetic material called PCA3 has been found in high levels in prostate tumor cells. Gen-Probe Inc has started clinical trials of a PCA3 prostate cancer test that may help determine the need for a repeat prostate biopsy.
* MabCure Inc, a Canadian biotechnology company, is developing an immune system molecule called a monoclonal antibody for early detection of prostate cancer.
Sources: American Cancer Society, National Cancer Institute
(Editing by Maggie Fox and Todd Eastham)