Definition of biochemical recurrence after radical prostatectomy does not substantially impact prognostic factor estimates

Purpose: Biochemical recurrence serves as a surrogate end point after radical prostatectomy. Many definitions of biochemical recurrence are currently used in the research literature. We examined various definitions in a large clinical cohort to explore whether estimation differs by definition.

Materials and methods: The cohort included 5,473 patients who underwent radical prostatectomy from 1985 to 2007 at our cancer center. Separate analysis was done with 12 definitions of biochemical recurrence used in published studies. Cox regression was done to estimate HRs for established predictors. Predictive accuracy was determined using the concordance index.

Results: Depending on the definition the recurrence-free probability was 86% to 91% at 3 years and 81% to 87% at 5 years. HRs tended to be smaller for the most inclusive definitions but were fairly similar across all definitions. The univariate HR was 2.1 to 2.4 for log prostate specific antigen, 2.4 to 2.6 for clinical stage T2b vs T2a or less and 9.8 to 15 for biopsy Gleason grade 8 or greater vs 6 or less. Multivariate HRs were more homogeneous across the definitions. The concordance index was 0.79 to 0.83 and 0.83 to 0.87 for the preoperative and postoperative nomograms, respectively.

Conclusions: Estimates of risk ratios and predictive accuracy are generally robust to the biochemical recurrence definition. For clinical research, groups using different definitions will come to similar conclusions on prognostic factors. The definition should be factored into studies comparing overall recurrence probabilities.