The CPC Risk Calculator: A New App to Predict Prostate-specific Antigen Recurrence During Follow-up After Radical Prostatectomy

Abstract

BackgroundIt can be challenging to predict the risk of biochemical recurrence (BR) during follow-up after radical prostatectomy (RP) in men who have undetectable prostate-specific antigen (PSA), even years after surgery. ObjectiveTo establish and validate a contemporary nomogram that predicts the absolute risk of BR every year after RP in men with undetectable PSA while accounting for competing risks of death. Design, setting, and participantsA total of 3746 patients from Rigshospitalet (Copenhagen, Denmark) and Stanford Urology (Stanford, CA, USA) who underwent RP between 1995 and 2013 were included. Outcome measurements and statistical analysisTime to BR was defined as the first PSA result ≥0.2 ng/ml. BR risk was computed using multiple cause-specific Cox regression including preoperative PSA, pT category, RP Gleason score (GS), and surgical margin (R) status. Death without BR was considered a competing event. The nomogram presents the future risk of BR for a man who is alive and without BR at the time of follow-up. Validation assessed the discrimination and accuracy using time-dependent area under the curve and Brier scores. Results and limitationsThe nomogram predicts risk of BR up to 12 yr after RP at an individual level. As example, the risk of BR for a man with pT3a, R−, GS 3 + 4, and preoperative PSA ≤10 ng/ml followed for 5 yr with undetectable PSA is 18% for the next 5 yr. External validation demonstrated both high accuracy and discrimination. The CPC Risk Calculator is available as a free Android and iOS App. Declining discrimination and accuracy after 7 yr of follow-up is the main limitation. ConclusionsThis nomogram can be used as a tool to inform men with undetectable PSA during follow-up after RP about their future risk of BR, and may aid in decisions on the necessity for further follow-up. The nomogram is the first to be available as a free app. Patient summaryWe developed an easily interpretable nomogram to evaluate the risk of prostate-specific antigen elevation (cancer recurrence) following complete removal of the prostate (radical prostatectomy). The tool can aid both physicians and patients in evaluating the future risk of cancer recurrence during follow-up after surgery. The model is available as a free mobile app that can be downloaded from the App Store.