Prostate Cancer Testing
Two new articles in the New England Journal of Medicine (Vol 360, p 1310, 2009 and same volume page 1320) together with an editorial (p 1351, same volume) present results of two long term studies, investigate whether PSA screening indeed reduces the death from prostate cancer. The U.S. study followed almost 77,000 men over a period of 7 years. The screening group had 6 years of PSA tests and 4 years of rectal exams. At the end of seven years, there were 2820 cancers in the creening group (1.16%) and 2322 (0.95%) in the control group. There were 2.0 deaths per 10,000 people in the screening group, and 1.7 in the control group. The conclusion - after 7 to 10 years of followup, the death rate from prostate cancer was very low, and did not differ meaningfully between the two groups.
The European study followed 182,000 men over about 9 years, and assigned randomly to a screening group that had PSA measured once evey four years, and a control group that did not have their PSA measured. The relative death rate of those in the screening group was 0.80, with a Margin of Error between 0.65 and 0.98. The difference between the risk for men who have PSA measured and those who don't translates into 0.71 additional deaths per 1000 men. Alternatively, 1410 men would need to be screened, and 48 additional cases of prostate cancer would need to be treated, in order to prevent one death. It is this high rate of overdiagnosis that is worrysome, because of the several unpleasant side effects of such treatment.
The editorial, summarizing these results states that PSA screening has at best a modest effect on prostate cancer mortality. This result comes at the cost of substantial overdiagnosis and overtreatment, leaving us with the question as to whether PSA screening does more good than harm. Indeed, this is a personal decision!