Variation in the use of postoperative radiotherapy among high-risk patients following radical prostatectomy

BACKGROUND: We used data from the Michigan Urological Surgery Improvement Collaborative (MUSIC) to investigate the use of adjuvant and salvage radiotherapy (ART, SRT) among patients with high-risk pathology following radical prostatectomy (RP). METHODS: For patients with pT3a disease or higher and/or positive surgical margins, we examined post-RP radiotherapy administration across MUSIC practices. We excluded patients with < 6 months follow-up, and those that failed to achieve a postoperative PSA nadir <= 0.1. ART was defined as radiation administered within 1 year post RP, with all post-nadir PSA levels < 0.1 ng ml(-1). Radiation administered > 1 year post RP and/or after a post-nadir PSA >= 0.1 ng ml(-1) was defined as SRT. We used claims data to externally validate radiation administration. RESULTS: Among 2337 patients undergoing RP, 668 (28.6%) were at high risk of recurrence. Of these, 52 (7.8%) received ART and 56 (8.4%) underwent SRT. Patients receiving ART were younger (P = 0.027), more likely to have a greater surgical Gleason sum (P = 0.009), higher pathologic stage (P < 0.001) and received treatment at the smallest and largest size practices (P = 0.011). Utilization of both ART and SRT varied widely across MUSIC practices (P < 0.001 and P = 0.046, respectively), but practice-level rates of ART and SRT administration were positively correlated (P = 0.003) with lower ART practices also utilizing SRT less frequently. Of the 88 patients not receiving ART and experiencing a PSA recurrence >= 0.2 ng ml(-1), 38 (43.2%) progressed to a PSA >= 0.5 ng ml(-1) and 20 (22.7%) to a PSA >= 1.0 ng ml(-1) without receiving prior SRT. There was excellent concordance between registry and claims data kappa = 0.98 (95% CI: 0.94-1.0). CONCLUSIONS: Utilization of ART and SRT is infrequent and variable across urology practices in Michigan. Although early SRT is an alternative to ART, it is not consistently utilized in the setting of post-RP biochemical recurrence. Quality improvement initiatives focused on current postoperative radiotherapy administration guidelines may yield significant gains for this high-risk population.