A matched control analysis of adjuvant and salvage high-dose postoperative intensity-modulated radiotherapy for prostate cancer

Abstract

Purpose: It is unclear whether immediate adjuvant radiotherapy for high-risk disease at prostatectomy (capsule perforation, seminal vesicle invasion, and/or positive surgical margins) is equivalent to delayed salvage radiotherapy at biochemical recurrence. We performed a matched case analysis comparing high-dose adjuvant intensity modulated radiotherapy (A-IMRT) with salvage IMRT (S-IMRT).

Methods and materials: One hundred forty-four patients with high-risk disease at prostatectomy were referred for A-IMRT, and 134 patients with high-risk disease were referred at biochemical recurrence (rising prostate-specific antigen [PSA], following prostatectomy, above 0.2 ng/ml) for S-IMRT. Patients were matched in a 1:1 ratio according to preoperative PSA level, Gleason score, and pT stage. Median doses of 74 Gy and 76 Gy were prescribed for A-IMRT and S-IMRT, respectively. We report biochemical relapse free survival (bRFS) rates using the Kaplan-Meier method. Univariate and multivariate analyses were used to examine tumour- and treatment-related factors.

Results: A total of 178 patients were matched (89:89). From the end of radiotherapy, the median follow-up was 36 months for both groups. The 3-year bRFS rate for the A-IMRT group was 90% compared to 65% for the S-IMRT group (p < 0.05). On multivariate analysis, S-IMRT, Gleason grades of ≥ 4+3, perineural invasion, preoperative PSA level of ≥ 10 ng/ml, and omission of androgen deprivation (AD) were independent predictors for a reduced bRFS (p < 0.05). From the date of surgery, the median follow-up was 43 and 60 months for A-IMRT and S-IMRT, respectively. The 3-year bRFS rate for A-IMRT was 91% compared to 79% for S-IMRT (p < 0.05). On multivariate analysis, Gleason grades of ≥ 4+3, perineural invasion, and omission of AD were independent predictors for a reduced bRFS (p < 0.05). S-IMRT was no longer an independent prognostic factor (p = 0.08).

Conclusions: High-dose A-IMRT significantly improves 3-year bRFS compared to S-IMRT. Gleason grades of ≥ 4+3, perineural invasion, and omission of AD were independent prognostic factors for a decreased bRFS, both from the dates of surgery and from radiotherapy.