Long-term Follow-up of a Matched Cohort Study Evaluating the Role of Adjuvant Radiotherapy for Organ-confined Prostate Cancer With a Positive Surgical Margin

OBJECTIVE To evaluate if adjuvant radiation therapy (ART) is associated with improved long-term oncologic outcomes for pT2N0R1 prostate cancer (PCa). METHODS Men with pT2N0 PCa and a single positive surgical margin following radical prostatectomy and pelvic lymphadenectomy were identified (1987-1996). Men who received ART were matched 1:1 to men who did not receive ART based on age, year of surgery, Gleason score, preoperative prostatespecific antigen, site of positive surgical margin, and DNA ploidy. Biochemical recurrence (BCR), local recurrence, distant metastasis, and overall survival (OS) were compared between groups in time-to-event analyses. RESULTS The cohort included 152 men (76 per group) with a median follow-up of 20 years (interquartile range 19,22). ART was associated with a lower cumulative incidence of BCR (25% vs 52%; P < .001) and local recurrence (3% vs 12%; P = .03), but no significant differences in cumulative incidence of distant metastasis (10% vs 7%; P = .44) or in probability of OS (56% vs 68%; P = .08) at 20 years. In competing risks models, receipt of ART was associated with reduced risks of BCR (hazard ratio [HR] = 0.40; 95% confidence interval [CI] 0.23-0.70; P < .001) and local recurrence (HR = 0.21; 95% CI.05-0.98; P = .05), but not distant metastasis (HR = 1.56; 95% CI 0.51-4.75; P = .43). In the Cox model, ART was not associated with improved OS (HR = 1.56; 95% CI 0.94-2.57; P = .08). CONCLUSION ART was associated with reduced risks of BCR and local recurrence for men with pT2N0R1 PCa. However, ART was not significantly associated with metastasis-free or OS benefits, as recurrences in these patients generally followed an indolent trajectory with 20 years of median follow-up. (C)2017 Elsevier Inc.