A population-based study of factors associated with post-prostatectomy radiation therapy utilization.

Abstract

182 Background: Based on level one evidence, adjuvant radiation therapy (aRT) improves cancer control in post-prostatectomy patients with adverse pathologic features. We sought to evaluate its utilization and to identify factors affecting of its use. Methods: Using the National Cancer Database, a joint project of the Commission on Cancer of the American College of Surgeons and the American Cancer Society, we identified men diagnosed with prostate cancer between 2004 and 2011 who were found to have pT3 disease or pT2 disease with positive margins following prostatectomy. We defined aRT as radiation to the prostate and/or pelvis 6 months or less after prostatectomy. We then used univariate and multivariate logistic regression models to assess potential patient and provider predictors of aRT use. Results: We evaluated 103,092 men who had either pT3 disease (81%) or pT2 with positive margins (19%). Of these, we identified 10,043 men (9.7%) who received aRT. Since 2004, there has been a steady decline in aRT usage with time (range, 11.5% to 7.8%). Compared to 2004, patients diagnosed in 2011 were significantly less likely to receive aRT (odds ratio [OR] 0.78, confidence interval [CI] 0.71-0.85, p<0.0001). Higher Gleason score and T stage were strongly associated with positive aRT utilization (p<0.0001), while increasing age was associated with decreased use (p<0.0001). Another strong predictor of aRT uptake was hospital type. Compared to patients treated at community hospitals, patients treated at comprehensive cancer centers or teaching hospitals were significantly less likely to receive aRT (OR 0.63, 0.58-0.68, p<0.0001 or OR 0.42, CI 0.39-0.46, p<0.0001, respectively). Charlson score and hospital location were significantly but weakly associated with aRT. Other demographic variables were not predictive of aRT. Conclusions: Post-prostatectomy aRT use is declining despite clear proof of its benefit. Consistent with the evidence, patients with risk factors for biochemical relapse (i.e. high Gleason score or T3 disease) and younger patients, who are more likely to benefit, are receiving aRT. Surprisingly, aRT use is lower at teaching hospitals, which may reflect higher usage of salvage radiation.