Digital rectal examination in the early detection of prostate cancer

Screening using digital rectal examination improves the clinical stage distribution of prostate cancer and prolongs survival. Unfortunately, digital rectal examination may not be sensitive enough to detect the small-volume tumors that are most amenable to cure. In several studies, approximately 50 per cent of cancers detected through screening had already spread beyond the prostate. Regardless, the key to demonstrating overall benefit from screening is a diminished disease-specific mortality rate. To date, this has not been shown. Lower mortality rates from prostate cancer can be demonstrated only through a randomized study comparing screened and unscreened populations. Such a study, which has recently been approved and funded by the National Institutes of Health, will require 10 to 15 years to complete. Until that time, the value of screening for prostate cancer by digital rectal examination or any other method will be unknown. Beyond a lack of proved benefit, screening for prostate cancer may be harmful because of the variable natural history of the disease and the morbidity and mortality rates associated with treatment. There exists a large population of patients with pathologically detectable prostate cancer who will never have clinical disease. The detection of some of these tumors may expose those patients to the risks of unnecessary treatment. Large-scale prostate cancer screening studies may ultimately be shown to be advantageous. The sooner this occurs, the earlier aggressive screening can be advocated, similar to screening for breast cancer. However, the temptation to embark on such screening programs without first demonstrating clear benefit should be resisted.