Postoperative prostate-specific antigen nadir improves accuracy for predicting biochemical recurrence after radical prostatectomy: Results from the Shared Equal Access Regional Cancer Hospital (SEARCH) and Duke Prostate Center databases

Objectives: We previously showed that prostate-specific antigen (PSA) nadir after radical prostatectomy (RP) significantly predicts biochemical recurrence (BCR). Herein, we sought to explore the effect of including PSA nadir into commonly used models on their accuracy to predict BCR after RP. Methods: This was a retrospective analysis of 943 and 1792 subjects from the Shared Equal Access Regional Cancer Hospital (SEARCH) and Duke Prostate Cancer (DPC) databases, respectively. The discrimination accuracy for BCR of seven previously published models was assessed using concordance index and compared with and without adding PSA nadir level in SEARCH. Using data from SEARCH, we developed a new nomogram incorporating PSA nadir to other known predictors (preoperative PSA, pathological Gleason score, PSA nadir level, surgical findings, prostate weight, body mass index and race) of BCR and externally validated it in the DPC. Results: In SEARCH, the mean concordance index across all seven nomograms was 0.687. After the inclusion of PSA nadir, the concordance index increased by nearly 7% (mean = 0.753). The concordance index of the new nomogram in SEARCH was 0.779 (bias-corrected = 0.767), which was 5% better than the next best model. In DPC, the new nomogram yielded a concordance index of 0.778. Conclusion: The addition of postoperative PSA nadir to commonly used nomograms increased their accuracies by nearly 7%. Based upon this, we developed and externally validated a new nomogram, which was well calibrated and highly accurate, and is a potentially valuable tool for patients and physicians to predict BCR after RP.