How accurate is a digital rectal exam?

A digital rectal exam (DRE) is clearly not perfect at detecting prostate cancer. Most prostate tumors begin in the posterior portion of the gland near the wall of the rectum, so the tumors can be examined in a rectal exam. But if a tumor is located away from the rectal wall, the physician will not be able to palpate it during a DRE. As a result, a significant proportion of men with a normal DRE may still have prostate cancer. For example, in one study of 6,630 men volunteering for DRE and prostate-specific antigen screening tests, 45% of the cancers that were detected were missed by the DRE. Other authors have reported finding cancer in 15% to 18% of men with a normal DRE.

If a lump is found, the chances are about 1 in 4 that it is cancerous. The more obvious the abnormality, the more likely it is to be cancer. But most cancers associated with clearly abnormal DREs are already advanced because smaller tumors are more difficult to feel. DRE is less effective than PSA at finding prostate cancer, but there are instances when cancers are found by DRE in men who have normal PSA levels. For this reason, both the DRE and PSA tests are recommended for men who choose to undergo screening for prostate cancer.

The effectiveness of the exam is somewhat dependent on the experience of the examiner. A more experienced clinician can detect subtle abnormalities that a less experienced clinician may overlook. Although the DRE has been used for many years, whether it actually decreases the number of deaths from prostate cancer has not been determined.