Predicting extraperitoneal ssRARP difficulty: an MRI-based nomogram

To develop and validate an MRI-clinical nomogram predicting surgical difficulty in extraperitoneal single-site robot-assisted radical prostatectomy (ssRARP). We retrospectively evaluated 252 patients undergoing extraperitoneal ssRARP. High difficulty was defined using cohort-specific ≥ 75th percentiles for console time (≥ 107.75 min) or estimated blood loss (≥ 50 mL). A nomogram was constructed via multivariable logistic regression and assessed using AUC, calibration plots, bootstrap validation, and decision curve analysis (DCA). High difficulty occurred in 124 patients (49.2%). Independent predictors included higher body mass index (OR = 1.122, P = 0.012), neoadjuvant therapy (OR = 1.972, P = 0.019), larger prostate volume (OR = 1.020, P = 0.003), narrower intertuberous distance (OR = 0.971, P = 0.043), and greater symphysis pubis height (OR = 1.071, P = 0.017). The nomogram showed acceptable discrimination (AUC = 0.675; optimism-corrected C-index = 0.650), good calibration, and positive DCA net benefit (13-92% thresholds). This novel nomogram optimizes patient selection and mitigates perioperative risks. However, because the difficulty thresholds were calibrated to our institution's specific cohort, recalibration is required before direct application to other centers.