Anatomic site-specific positive margins in organconfined prostate cancer and its impact on outcome after radical prostatectomy

Abstract

The impact of a positive surgical margin in otherwise confined prostate cancer after radical prostatectomy remains unclear. We analyzed the outcome of a large number of patients with organ-confined prostate cancer according to the presence and anatomic site of margin positivity. We evaluated 2712 prostatectomy patients with Stage pT2N0 cancer (ie, no evidence of extra-prostatic disease, seminal vesicle or regional node involvement) and no prior therapy who were treated by radical prostatectomy between 1987 and 1995 at Mayo Clinic. A total of 697 patients (26%) had positive margins. To assess the effect of margin status in the absence of treatment, 378 patients with postoperative adjuvant therapy were not considered for the study group: the final group consisted of 2334 patients. Overall, 253 (58%) tumors were positive at the apex and/or urethra, 85 (19%) at the prostate base, 11 (2.5%) at the anterior prostate, and 174 (40%) at the posterior prostate; 89 (20%) had at least two margins involved and 21 (8.3%) had more than two involved. The apex/urethra was the only positive anatomic site in 183 (42%). Five-year survival free of clinical recurrence or prostate-specific antigen (PSA) biochemical failure (postoperative serum PSA of 0.2 ng/mL or more) for patients with a single positive margin was 79% for apex or urethra, 78% for anterior/posterior, and 56% for prostate base. Five-year survival free of clinical recurrence or PSA (biochemical) failure was slightly higher for those with one versus two margin-positive regions (77% versus 68%, respectively). Multivariate analysis revealed that positive surgical margins were a significant predictor of clinical recurrence and PSA (biochemical) failure (relative risk [95% confidence interval]: 1.65 [1.24, 2.18]) after controlling for Gleason grade, preoperative PSA, and deoxyribonucleic acid (DNA) ploidy. The effect of margin positivity on recurrence at a specific anatomic site (versus negative margins or positive at a different anatomic site) revealed the prostate base to be the only significant anatomic site when adjusted for grade, PSA, and ploidy. Five-year survival free of the combined clinical or PSA failure end point for those with versus those without positive margins at the prostate base was 56% versus 85%, respectively (P < 0.0001). Positive surgical margins are a significant predictor of recurrence in Stage pT2N0 cancer, which is independent of grade, PSA, and DNA ploidy. The impact of positive margin status on recurrence-free survival appears to be anatomic and site-specific, with prostate base positivity significantly associated with poor outcome. The benefit of adjuvant therapy based on anatomic site-specific margin positivity remains to be tested in order to optimize recurrence-free survival.