Hereditary prostate cancer

Canadian Medical Association Journal 1996; 154: 300-301

[Letters]

As Ms. Dawn L. McLellan and Dr. Richard W. Norman noted in the article "Hereditary aspects of prostate cancer" (Can Med Assoc 1995; 153: 895­900), prostate cancer is now the second most common type of cancer among Canadian men after skin cancer. According to projections made before testing for prostate-specific antigen (PSA) levels was available in Canada, there will be 35 200 new cases diagnosed annually by the year 2016.[1] Unfortunately, as McLellan, Norman and Dr. J. Curtis Nickel ("The dilemma of hereditary prostate cancer," CMAJ 1995; 153: 935­938) point out, there are no primary prevention strategies to lower the risk of this disease. Thus, the potential lies in early detection and treatment.

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

  1. Morrison HI, MacNeill IB, Miller D et al: The impending Canadian prostate cancer epidemic. Can J Public Health 1995; 86: 274­278
  2. Minutes of National Board of Directors Meeting, Canadian Cancer Society, Toronto, Oct 15­16, 1994
  3. Minutes of National Board of Directors Meeting, National Cancer Institute of Canada, Toronto, Oct 21­22, 1994
  4. Collins JP: Detection of prostate cancer. [letter] CMAJ 1995; 152: 328­329
  5. Feightner JW: Screening for prostate cancer. In Canadian Guide to Clinical Preventive Health Care, Health Canada, Ottawa, 1994: 812­823
  6. Schröder FH: Detection of prostate cancer: Screening the whole population has not yet been shown to be worth while. BMJ 1995; 310: 140­141
  7. Krahn MD, Mahoney JE, Eckman MH et al: Screening for prostate cancer: a decision analytic view. JAMA 1994; 272: 773­780
| CMAJ February 1, 1996 (vol 154, no 3) |