Relationship of Positive Resection Margin, Cancer Location and Learning Curve after Laparoscopic Radical Prostatectomy

Background: One of surgical goals is decreasing of positive resection margin (PRM). In radical prostatectomy, PRM is important because of prognostic factor. We examine the relationship of PRM, cancer location and learning curve after laparoscopic radical prostatectomy (LRP). Methods: Between May, 2009 and May, 2015, 331 consecutive patients were treated with LRP. The resection margin status, Gleason score, pathological stage, cancer location and diameter were assessed in each surgical specimen, and the independent factors for PRM and prostate-specific antigen (PSA) failure were identified. The learning curve for PRM was calculated and the number of cases until the plateau was obtained. Results: PRM was found in 30.5% of all patients, with 27.7% in the pT2 patients and 39.0% in the pT3 patients. The most common site of PRM was in the apex-anterior. The 5-year PSA failure-free survival rate was 73.9%. In patients with a negative resection margin, the 5-year PSA failure-free survival rate was 81.6%, and in patients with PRM, it was 57.4%. The factors associated with PSA failure-free survival were PRM and elevated PSA. The tumor location was not associated with PSA failure-free survival. The factors associated with PRM were tumor location, nerve sparing procedure, and tumor diameter. When the tumor was localized in the apex-anterior, the rate of PRM was elevated 3-fold comparing the tumor in apex-posterior. The learning curve of all surgeons for obtaining a negative resection margin plateaus after 167 cases. The curve of a single surgeon was more improved than all surgeons and the rate of PRM was 16.7%. Conclusions: PRM was associated with both cancer location and diameter. The learning curve of PRM reached a plateau in about 170 cases. However, PRM can be further reduced. These findings related to LRP outcomes are useful for improvement in surgical techniques and for determining prognosis.