Radiotherapy after prostatectomy: improved biochemical relapse-free survival with whole pelvic compared with prostate bed only for high-risk patients

Abstract

Purpose: To compare the biochemical relapse-free survival (bRFS) among patients receiving whole pelvic radiotherapy (WPRT) vs. prostate bed RT (PBRT) after radical prostatectomy.

Methods and materials: Between 1985 and 2005, 160 patients underwent adjuvant or salvage RT after radical prostatectomy. A short course of total androgen suppression was also given concurrently to 87 patients. Of the 160 patients, 114 were considered at high risk of lymph node involvement because they had a pathologic Gleason score of >/=8, a preoperative prostate-specific antigen level >20 ng/mL, seminal vesicle or prostate capsule involvement, or pathologic lymph node involvement. Of this group, 72 underwent WPRT and 42 underwent PBRT. The median follow-up was >5 years for all patient subsets. Kaplan-Meier and Cox proportional hazards multivariate analyses were performed for all clinical, pathologic, and treatment factors predicting for bRFS.

Results: Whole pelvic RT resulted in superior bRFS compared with PBRT (p = 0.03). The advantage of WPRT was limited to high-risk patients, with a 5-year bRFS rate of 47% (95% confidence interval, 35-59%) after WPRT vs. 21% (95% confidence interval, 8-35%) after PBRT (p = 0.008). For low-risk patients, no difference (p = 0.9) was found. On multivariate analysis, only WPRT (p = 0.02) and a preoperative prostate-specific antigen level <1.0 ng/mL (p = 0.002) were significantly associated with bRFS. The benefit from total androgen suppression with postoperative RT was only observed when given concurrently with WPRT (p = 0.04) and not with PBRT (p = 0.4).

Conclusion: The results of our study have indicated that WPRT confers superior bRFS compared with PBRT for high-risk patients receiving adjuvant or salvage RT after radical prostatectomy. This advantage was observed only with concurrent TAS. These results are analogous to the benefit from WPRT seen in the Radiation Therapy Oncology Group 94-13 study.