Positive margin length and highest Gleason grade of tumor at the margin predict for biochemical recurrence after radical prostatectomy in patients with organ-confined prostate cancer

Background: To evaluate the pathologic features after radical prostatectomy to determine if the length of positive surgical margin (PSM) and the highest Gleason grade within the tumor at the PSM could risk stratify patients for biochemical recurrence (BCR). Methods: We performed a retrospective, matched, cohort study to identify patients with pathologically organ-confined (pT2) tumors and negative nodes (pN0/Nx), receiving no adjuvant therapy. Specimens underwent single pathologist review. BCR-free survival was estimated using the Kaplan-Meier method and compared between subgroups using two-sided log-rank test. Using Classification and Regression Tree analysis (CART), we identified an optimal cutoff for the PSM length which differentiated risk for BCR. Cox proportional hazards regression models were fit to assess the association between variables and BCR-free survival. Results: Two-hundred PSM patients were matched to 200 patients with negative surgical margins (NSM). Median follow-up was 64 months. 5 year BCR-free survival was 90% (95% CI 84-97%) in the NSM group and 70% (95% CI 63-79%) in the PSM group. There was an increased risk of BCR with any PSM. Multivariable analysis demonstrated an association with length of PSM (> 1 mm vs. ≤ 1 mm, HR 2.29; 95% CI 1.2-4.5) and having a highest Gleason grade of the cancer focus at the margin ≥ 4 (HR 6.8; 95% CI 1.6-29). Conclusions: We demonstrated that patients with pathologic T2 tumors with PSM > 1 mm or a Gleason grade of tumor focus at the margin ≥ 4 are at elevated risk for BCR. However, this study suggests that patients with pT2 tumors with positive surgical margins have a relatively low risk of biochemical recurrence and adjuvant radiation may be over treating this sub population. The subsets at greatest risk for BCR may benefit from more frequent PSA monitoring to direct salvage therapies.