Mortality reductions produced by sustained prostate cancer screening have been underestimated

Abstract

Background The recently published European Randomized Study of Screening for Prostate Cancer (ERSPC) reported prostate specific antigen (PSA)-based screening to have reduced the prostate cancer death rate by only 20%. However, this is an underestimate caused by (i) including in the 20% the years before the impact of the first screen becomes manifest, and (ii) not having full information for the follow-up years where the effects of the screening are most apparent. This paper provides a re-analysis of the results using time-specific measures, which avoid the first of these sources of error. Methods Mortality rate ratios for follow-up years 1-12 were derived from the yearly numbers of prostate cancer deaths and numbers of men being followed in each arm of the ERSPC. To reduce statistical noise, they were based on moving three-year intervals, and a smooth rate ratio curve was fitted to the yearly data, in order to measure the steady state reduction in mortality and to identify the time at which it reached this level. Results The re-analysis suggests that the sustained reduction in prostate cancer mortality may be more than 50%. Conclusion Re-analysis of the ERSPC data suggests that if screening is carried out for several years, and if follow-up is pursued until the reduction becomes manifest, the reduction in mortality will be 50-60%. An analysis that includes the 2007-2008 follow-up data is required to quantify more precisely the impact of this intervention.