Development and validation of novel nomogram to identify the candidates for extended pelvic lymph node dissection for prostate cancer patients in the robotic era

To determine candidates for extended pelvic lymph node dissection using a novel nomogram to assess the risk of lymph node invasion in Japanese prostate cancer patients in the robotic era.A total of 538 patients who underwent robot-assisted radical prostatectomy with extended pelvic lymph node dissection in three hospitals were retrospectively analyzed. Medical records were reviewed uniformly and the following data collected: prostate-specific antigen, age, clinical T stage, primary and secondary Gleason score at prostate biopsy, and percentage of positive core numbers. Finally, data from 434 patients were used for developing the nomogram and data from 104 patients were used for external validation.Lymph node invasion was detected in 47 (11%) and 16 (15%) patients in the development and validation set, respectively. Based on multivariate analysis, prostate-specific antigen, clinical T stage ≥3, primary Gleason score, grade group 5, and percentage of positive cores were selected as variables to incorporate into the nomogram. The area under the curve values were 0.781 for the internal and 0.908 for the external validation, respectively.The present nomogram can help urologists identify candidates for extended pelvic lymph node dissection concomitant with robot-assisted radical prostatectomy among patients with prostate cancer.