No one doubts that screening reduces death from breast and colon cancer. However, the effectiveness of prostate cancer screening is still being debated. The degree of enthusiasm for prostate cancer screening and treatment seems high given the limited evidence of benefit and well-documented harms of treatment, according to the Patient Outcomes Research Team (PORT) for Prostatic Diseases.
Two recent PORT studies, supported by the Agency for Healthcare Research and Quality (HS08397), examine the benefits of prostate cancer screening and treatment. The first study concluded that steps should be considered to temper possible overenthusiasm for screening and treatment. The second study found that more intensive screening and treatment among Medicare patients in one State compared with another was not associated with lower prostate cancer-related deaths over 11 years.
Ransohoff, D.F., Collins, M.M., and Fowler, F.J. (2002, December). "Why is prostate cancer screening so common when the evidence is so uncertain? A system without negative feedback." American Journal of Medicine 113, pp. 663-667.
It may be time to take steps to temper possible overenthusiasm for prostate cancer screening and treatment, according to Prostate PORT investigators. In this study, they reviewed research studies to understand the reasons for the enthusiasm and positive reinforcement perceived in clinical decisions about whether to screen for prostate cancer, whether to choose aggressive therapy for cancer, and how to view adverse effects following therapy. They discuss the case of a man who must decide about screening and treatment to illustrate the kinds of reinforcement that may occur for each decision. They point out that strong positive reinforcement for each decision makes screening and aggressive therapy appear to be successful and the correct decision, even if prostate cancer screening and therapy are not beneficial.
Prostate-specific antigen (PSA) screening tests that yield false-positive results (indicate cancer when there is no cancer) can lead to anxiety and repeated biopsies. About 60 percent of men who undergo radical prostatectomy (surgical removal of the prostate) cannot have an erection, and 30 percent need to wear pads to deal with leaking urine. These relatively common and dramatic personal harms of screening and treatment are readily discounted or explained away. The physician is positively reinforced for recommending screening, regardless of the test result. A negative result makes a patient grateful for reassurance, and a positive result makes a patient grateful for early detection. A patient who is impotent and incontinent after a decision for curative treatment may attribute his survival to surgery and be grateful for having his cancer cured.
Whether or not early detection and aggressive treatment of prostate cancer reduces prostate cancer mortality is still not known, stress the researchers. They suggest several ways to curb possible overenthusiasm for aggressive screening and treatment for prostate cancer. One approach is to require that patients complete detailed written informed consent before screening, indicating an understanding that evidence of efficacy is weak or lacking and that adverse effects may occur. By ensuring that patients are informed about the pros and cons of testing and its consequences before they are tested, the chances are much improved that doctors and their patients will make decisions that are not tipped, possibly quite unfairly, toward intervention.
Lu-Yao, G., Albertsen, P.C., Stanford, J.L., and others. (2002, October). "Natural experiment examining impact of aggressive screening and treatment on prostate cancer mortality in two fixed cohorts from Seattle area and Connecticut." British Medical Journal 325, p. 740.
This study reinforces the uncertain value of aggressive screening and treatment of prostate cancer. The researchers found that the more intensive screening and treatment for prostate cancer in one area over another was not associated with lower prostate cancer-related deaths over 11 years of followup. The researchers examined the rates of screening for prostate cancer, treatment with radical prostatectomy and radiation, and prostate cancer-related deaths from 1987 to 1997 among Medicare beneficiaries aged 65-79 drawn from the Seattle-Puget Sound area and Connecticut.
The prostate-specific antigen (PSA) testing rate in the Seattle area was 5.39 times that of Connecticut, and the prostate biopsy rate was 2.20 times that of Connecticut during 1987-1990. The 10-year cumulative incidence's of radical prostatectomy and external beam radiotherapy up to 1996 were 2.7 percent and 3.9 percent for Seattle men compared with 0.5 percent and 3.1 percent for Connecticut men. Yet, the adjusted rate of prostate cancer-related deaths up to 1997 was similar for Seattle and Connecticut.
Moreover, the overall drop in prostate cancer mortality seemed similar in the two regions. The researchers point out, however, that only elderly men were included in this study, and screening and treatment for prostate cancer may have a larger impact on younger men. However, prostate cancer death is rare before age 70. If recent decreases in prostate cancer mortality in the United States are attributable to screening and treatment with surgery and radiation, this impact would almost certainly be seen among Medicare age men. The researchers suggest continuing clinical trials to establish the value of aggressive screening and treatment for this condition.