For instance, PSA density relates a man's PSA level to the size of his prostate, which can be estimated through ultrasound. In the case of a benign enlargement, there is more free PSA, while cancer produces more of the attached form, although the reasons for this difference are not well understood. As for DRE, this test is most accurate when performed by a doctor who is highly skilled in such a procedure. But the procedure does have problems, often missing many small cancers, especially cancers toward the front of the prostate gland or deep within it. The exam also is notoriously unpopular among men and even among some doctors.
Many men say they find the test embarrassing and uncomfortable.
Studies also suggest that some physicians are reluctant to do rectal exams. So far, it has not been possible to distinguish these slow-growing tumors from tumors that are aggressive and deadly. What is known is that treatment can have serious side effects, some of which are permanent. Cancer Screening Trial . Some 37,000 men ages 55 to 74 are being screened, and those positive on either PSA or DRE will receive a diagnostic followup.