There are screening tests for prostate cancer. One is the digital rectal exam (DRE). The doctor insertS a gloved finger into the rectum to “feel” the prostate gland for abnormalities. The second screening tool is the PSA blood test. PSA (prostate specific antigen) is a protein produced by the prostate gland.
High levels of PSA in the blood are associated with prostate cancer. However, it’s not a perfect test. An elevated PSA can also be caused by benign prostate enlargement, infection or inflammation of the prostate gland and use of some medications. In addition, some men with prostate cancer have normal PSA levels.
Since screening tests aren’t 100 percent reliable, doctors may recommend a biopsy when they suspect a patient has prostate cancer. In this procedure, a needle is placed into the prostate gland to remove small amounts of tissue. Then the cells are examined for abnormalities indicating the presence of cancer. A biopsy is considered to be the gold standard for cancer diagnosis. But even this test isn’t perfect. Initially, the cancer is usually confined to small areas of the prostate gland. When the biopsy needle is inserted into the prostate, it may miss the area(s) containing cancer and only retrieve normal cells.
Shane Rogosin, M.D., a Cancer Researcher with OHSU (Oregon Health & Science University) Cancer Institute, says a biopsy can miss up to a third of prostate cancers. Thus, a man with an elevated PSA level and abnormal DRE can still have a normal biopsy. If doctors are still suspicious about possible prostate cancer, there are two options. The first is a second biopsy. Hopefully, if prostate cancer is present, the needle will reach the right area and retrieve cancer cells. The second option is to wait.
Prostate cancers usually grow very slowly. In fact, some patients who are diagnosed with the cancer are offered a “watch and wait” treatment. But if the cancer is aggressive, it could quickly spread before the next examination.
Researchers at OHSU have recently found a technique which may be useful in predicting which men with a negative biopsy may benefit most from a second biopsy. They use a tool called PSA density. PSA density is a measurement which compares a man’s PSA level with the volume of his prostate gland. Men with the highest PSA densities are more likely to be later diagnosed with aggressive prostate cancers.
Rogosin says if a PSA density is high, doctors can feel more assured of the need for a repeat biopsy. If, however, the PSA density level is low, there is less chance of an aggressive form of prostate cancer and doctors may be able to spare the patient the need for an immediate second biopsy.