Predictors of recurrence after robotic prostatectomy for pT3b disease
Ibrahim Ibrahim, Luke Thompson, Sanjana Ilangovan, Sarika Nalagatla, Lorenzo Dutto, Bilal Ibrahim, Imran AhmadBackground:
Seminal vesicle invasion (pT3b disease) is a strong predictor of poor oncological outcomes in prostate cancer. The role of robotic-assisted laparoscopic prostatectomy in this setting remains debated, and the accuracy of multiparametric magnetic resonance imaging in staging T3b disease remains uncertain. The primary aim of this study was to identify pre- and postoperative predictors of biochemical recurrence in pT3b prostate cancer treated with robotic-assisted laparoscopic prostatectomy using time-to-event survival analysis. The secondary aim was to evaluate the diagnostic accuracy of multiparametric magnetic resonance imaging in staging seminal vesicle invasion.
Methods:
Patients with pathological T3b disease were identified retrospectively from a prospectively maintained institutional robotic-assisted laparoscopic prostatectomy database (December 2015 to August 2023). Data included demographics, preoperative variables, and pathological findings. Biochemical recurrence was defined as prostate-specific antigen ⩾0.1 ng/mL on two consecutive occasions. Biochemical recurrence-free survival was estimated using the Kaplan–Meier method, and univariate and multivariate Cox proportional hazards regression models were used to identify predictors of recurrence. A subgroup of patients staged as cT3b on multiparametric magnetic resonance imaging was compared with pathological outcomes to assess staging accuracy, with 95% confidence intervals calculated for sensitivity and specificity estimates.
Results:
Of 149 patients with pT3b disease, 146 were included in the descriptive clinicopathological analysis after exclusion of duplicate or inconsistent records. Of these, 139 had complete time-to-event data and were included in the survival analysis. Seventy-three patients (52.5%) developed biochemical recurrence during a median follow-up of 20.5 months, with a median time to biochemical recurrence of 3.6 months. The Kaplan–Meier analysis demonstrated a median biochemical recurrence-free survival of 31.4 months. On univariate Cox regression, higher Grade Group (hazard ratio = 1.27, 95% confidence interval = 1.03–1.55; p = 0.022), positive surgical margins (hazard ratio = 2.24, 95% confidence interval = 1.40–3.59; p < 0.001), and positive lymph nodes (hazard ratio = 1.84, 95% confidence interval = 1.05–3.21; p = 0.033) were significant predictors of biochemical recurrence, whereas age, prostate-specific antigen, and prostate size were not. On multivariate analysis, positive surgical margins remained the only independent predictor (hazard ratio = 2.20, 95% confidence interval = 1.18–4.09; p = 0.013). Of 53 patients staged as cT3b on multiparametric magnetic resonance imaging, 37.7% were downstaged to pT3a, and 3.8% were upstaged to pT4. T2-weighted imaging showed high sensitivity (96.6%, 95% confidence interval = 82.8–99.4%) but low specificity (26.1%, 95% confidence interval = 12.5–46.5%) for seminal vesicle invasion.
Conclusion:
In pT3b prostate cancer treated with robotic-assisted laparoscopic prostatectomy, positive surgical margins are the strongest independent predictor of biochemical recurrence, with Grade Group and nodal status providing additional prognostic value on univariate and Kaplan–Meier analysis. Preoperative prostate-specific antigen, age, and prostate volume were not associated with recurrence. Multiparametric magnetic resonance imaging frequently overstages seminal vesicle invasion, and treatment decisions should incorporate integrated radiological and pathological assessment. These findings support early consideration of salvage or adjuvant therapy in patients with positive margins.