From 1992-2001, 7 countries in Europe gradually recruited men for the European Randomised Screening for Prostate Cancer (ERSPC) trial. Centres recruit different age groups and have different designs for recruiting and countries have different underlying risks for prostate cancer. Recruitment has reached 163,126 men aged 55-69 at entry now. Our purpose was to calculate the power of the trial and at what point in time can statistically significant differences in prostate cancer mortality be expected. Recruitment data were collected from the screening centres. We calculated the expected number of prostate cancer deaths in each follow-up year, based on national statistics and expected rate in trial entrants. The power was calculated using different assumptions on intervention effect and contamination rate and also if the ERSPC trial would cooperate with other trials. With an assumed 25% intervention effect in men actually screened and a 20% contamination rate, the trial will reach a power of 0.86 in 2008. With an assumed intervention effect of 40%, the power reaches 0.90 in 2003-2004. Pooling data with those of the Prostate, Lung, Colorectal and Ovary (PLCO) trial early is expected to improve the power to 79% (20% intervention effect) to 92% (40% intervention effect PLCO). Adding more centres with compliance rates lower than 45% decreases the power of the trial. The ERSPC trial has sufficient power to detect a significant difference in prostate cancer mortality between the 2 arms if the true reduction in mortality by screening is 25% or more or if contamination remains limited to 10% if the true effect is 20% or more. If early detection and treatment turns out to have a stronger effect as may be suggested by observational data, the ERSPC trial is likely to conclusively show that within the next 5 years.
Copyright 2001 Wiley-Liss, Inc.