Canadian Medical Association Journal 1996; 154: 300-301
Yet, as Nickel notes, several Canadian agencies have concluded, on the basis of available evidence, that men with no symptoms should not be screened, except within the context of a randomized trial.[25] This recommendation has been made because there is no evidence that early detection and treatment leads to a decreased risk of dying of the disease.[6] Furthermore, the diagnostic work-up following a positive result of a screening test and the treatment following confirmation of cancer have risks and are expensive. Unnecessary anxiety and iatrogenic illness may result from a false-positive test result, and false reassurance from a false-negative result. Thus, quality of life may be decreased while more societal resources are used, with little overall benefit.[7]
Given the increasing evidence of a hereditary component of prostate cancer, McLellan, Norman and Nickel note that refinements in current screening practices are expected and desirable. These authors fail to point out, however, that the effectiveness of early detection tools in screening asymptomatic relatives of men with prostate cancer has not been shown. The arguments against screening apply whether or not men have a family history of prostate cancer. Screening high-risk groups (first-degree relatives of men with prostate cancer, in this case) is theoretically of greater benefit than mass screening because of the higher positive predictive value of the test results. However, the benefit of testing men at high risk who have no symptoms, whether we call it "screening" or "early case detection," remains unproven, and it may be harmful.
We must convey this message of uncertainty to our patients, and we must support studies that can inform this debate. A multicentre randomized controlled trial to evaluate the effectiveness of screening with the PSA test is being planned. The Laboratory Centre for Disease Control, Health Canada, strongly supports such a trial and calls on the profession to support proper evaluation of new technologies before widespread acceptance in medical practice.
Isra Levy, MD, BCh, MSc, FRCPC
Medical consultant
Ann Coombs, MSc
Epidemiology consultant
Cancer Bureau
Laboratory Centre for Disease Control
Health Canada
Ottawa, Ont.
References