Extent of prostate-specific antigen contamination in the Spanish section of the European Randomized Study of Screening for Prostate Cancer (ERSPC)

OBJECTIVES: The performance of tests outside prostate cancer screening trials (PSA contamination) may affect their statistical power. The present study addressed the extent of PSA contamination in the Spanish section of the European Randomized Study of Screening for Prostate Cancer (ERSPC) and its impact on biopsy performance and prostate cancer detection. METHODS: Data linkage was performed to address screening-related interventions outside the study. Four databases were used: (1) Spanish ERSPC database (n=4278), (2) laboratory database with all PSA determinations (n=31,140), (3) database of 1608 prostate biopsies, and (4) records of all prostate cancers (n=819) diagnosed at our centre. PSA contamination, biopsy performance, and cancer detection rates were calculated. RESULTS: Median follow-up time was 6.6 yr. A total of 2201 PSA determinations were performed for 1253 men. Cumulative PSA contamination was 29.3% (17% in the control arm during the first 4 yr). A higher proportion of men undergoing biopsies was found in the screening arm (21.3% vs. 2.9% in the control arm, p<0.0001). Similarly, higher cancer detection rates were found in the screening (4.7% vs. 1.2% in the control arm, p<0.0001). CONCLUSIONS: In our experience, the PSA contamination rate has increased during the last years, but its impact on biopsy performance and cancer detection in the control arm of the trial is limited and not likely to compromise the statistical power of the ERSPC trial.