Location and number of positive surgical margins as prognostic factors of biochemical recurrence after salvage radiation therapy after radical prostatectomy

Objective: To determine if the location and number of positive surgical margins (PSMs) after radical prostatectomy (RP) are associated with recurrence after salvage external beam radiation therapy (sEBRT).

Patients and methods: We retrospectively reviewed the medical records of 60 patients with PSMs who underwent three-dimensional conformal sEBRT for biochemical recurrence (BCR) or clinically detected local recurrence after RP between 1996 and 2007. PSMs were categorized as present or absent at three locations, and patients were classified as having either one or more than one PSM. BCR after RP was defined as a prostate-specific antigen (PSA) level of ≥ 0.1 ng/mL. BCR after sEBRT was defined as a serum PSA level of ≥ 0.1 ng/mL above the PSA nadir after sEBRT.

Results: In all, 24 (40%) patients had more than one PSM. Overall, the most common location of a PSM was the posterior prostate with 40 (66%) patients having a positive posterior margin. The location of PSMs was not significantly associated with secondary BCR (global P= 0.8). There was a borderline result between the number of PSMs and BCR: men with more than one PSM were less likely to recur compared with those with only one PSM (hazard ratio 0.42; P= 0.067).

Conclusions: This is the first study to specifically analyse location and number of PSMs as prognostic factors for men who undergo sEBRT. There was no evidence to suggest that the location of a PSM predicted secondary BCR. Further research is needed to determine whether the number of PSMs is an important predictor of BCR after sEBRT.