The association between nerve sparing and a positive surgical margin during radical prostatectomy.

PURPOSE A positive surgical margin (SM) during radical prostatectomy (RP) increases risk of biochemical recurrence. We evaluated the effect of nerve-sparing procedures on risk of positive SM for pT2- and pT3-category tumors. We hypothesized that nerve sparing would increase rates of pT2 positive margins. METHODS We evaluated a historical cohort of 9,915 consecutive RP patients treated at The Ottawa Hospital or Memorial Sloan-Kettering Cancer Center from 2000 to 2010. Patients underwent open, laparoscopic, or robotic RP. The primary outcome was presence of a positive SM stratified by pathologic pT2 and pT3 categories. The association between nerve sparing and positive margin was adjusted for prostate-specific antigen, RP Gleason sum, surgical modality, surgical date, and location in the multivariable model. RESULTS Of 6,120 eligible patients, 3,958 (64.7%) had open RP, 1,566 (25.6%) had laparoscopic RP, and 596 (9.7%) had robotic RP. Approximately 8.6% (363/4,199) of patients with pT2-category disease and 25.2% (485/1,921) of patients with pT3-category disease had a positive margin. Patients with pT2-category disease who underwent a bilateral nerve-sparing procedure were more likely to have a positive margin when compared with those who underwent nerve resection on multivariable analysis (relative risk [RR] = 1.52, 95% CI: 0.97-2.39) after adjusting for confounders. Patients with pT3-category disease who underwent a bilateral nerve-sparing procedure had no associated increase in risk of positive margin after adjustment for other variables (RR = 0.96, 95% CI: 0.80-1.16). Prostate incision into tumor (pT2R1) was significantly more likely in patients treated with robotic surgery (RR = 1.76, 95% CI: 1.25-2.48) than in those with open surgery. There was no difference between laparoscopic and open RP (RR = 0.86, 95% CI: 0.65-1.12). CONCLUSIONS Bilateral nerve sparing is associated with increased risk of positive SMs in patients with pathologic T2-category disease during RP.