to the editor: I was disturbed by the conclusions made in this article concerning prostate cancer screening. The Lancet study1 cited was chosen as one of the 251 studies that “had the potential to change practice if valid,” and as one of the top 20 studies “judged to have the greatest clinical relevance for family physicians.”
Let's suppose that the data from this study are valid. The clinical question posed is, “Are men who are invited to receive systematic prostate cancer screening better off than men who receive routine care?” The bottom-line answer provided is that “One would have to screen approximately 800 men to prevent one from dying of prostate cancer.” I do not believe that this supports the authors' conclusion that “prostate cancer screening provides a very small benefit, which is outweighed by significant potential harms of screening and associated follow-up treatment.”
This conclusion will no doubt impact the decision making of many practicing physicians, but there is a danger of impersonalization inherent in reaching conclusions based solely on statistical data.
For another perspective, imagine sitting in a crowded football stadium with 100,000 men in the stands who have all been screened for prostate cancer. At halftime, all men whose lives were saved in the past 12 months because of prostate cancer screening are invited to come onto the field. According to the statistics derived from The Lancet study, there are now 125 men (100,000/800) enjoying a football game who would have been dead without screening. How many of the other men in the crowd would conclude that screening is only of little benefit and be inclined to forgo future screening for themselves? I hope family physicians reject practice-changing conclusions based only on “valid data” that ignore the value of individual lives lost because of nifty statistical analysis.
in reply: First, it is important to point out that we did not choose the top 20 research studies for our report; they were selected by thousands of members of the Canadian Medical Association who vote on the impact that each study has on their practice.
Second, Dr. Jones focuses entirely on the potential benefits of prostate cancer screening at the population level and disregards the harms. This is inappropriate, because when we are beginning with a population of asymptomatic men, it is particularly important that the process of screening, biopsy, and treatment does not do more harm than good. Unfortunately, the potential harms of screening for prostate cancer are well established. Based on data summarized by the Canadian Task Force on Preventive Health Care,1 those 125 men would be joined on the field by more than 10,000 men who undergo treatment for prostate cancer, of whom about one-third never would have experienced symptoms or illness from the disease. Of those men, approximately 1,700 will experience urinary incontinence, 2,800 will experience long-term erectile dysfunction, and 40 to 50 will die from complications of prostate cancer treatment. These harms may be partially mitigated if more men opt for active surveillance or watchful waiting, although it is unclear to what extent.
Finally, we are not aware of any organization that recommends population screening for prostate cancer in all men in a certain age range. The American Urological Association2 and the American College of Physicians3 recommend that physicians discuss the potential benefits and harms of screening in men 55 to 69 years of age, but they do not recommend screening for all men in that age range. The Canadian Task Force1 and the U.S. Preventive Services Task Force4 recommend against screening for prostate cancer.