MP78-10 CONTEMPORARY USE OF ADJUVANT AND SALVAGE RADIOTHERAPY FOLLOWING RADICAL PROSTATECTOMY IN THE STATE OF MICHIGAN

Abstract

INTRODUCTION AND OBJECTIVES: Clinical trial evidence and ASTRO/AUA guidelines support the use of adjuvant radiotherapy (aXRT) for select high-risk men who have undergone radical prostatectomy (RP). Reports suggest, however, that utilization of aXRT remains low. We sought to understand the current practice patterns regarding the use of aXRT among patients in Michigan with high-risk pathological features after RP. Additionally, we examined whether early salvage XRT (sXRT) is being utilized as an alternative strategy. METHODS: From a prospective cohort of patients undergoing RP between 3/2012-3/2014 by urologists participating in the Michigan Urological Surgery Improvement Collaborative (MUSIC), we identified all patients with final pathology showing pT3a disease or higher (pT3þ) and/or positive surgical margins (PSM). We excluded patients who failed to achieve a post-operative PSA nadir 0.1, patients with lymph node metastasis, and patients with <6 months of follow-up. We then examined the variation in the use of postoperative XRT according to patient characteristics and across MUSIC practices. RESULTS: Among 2,342 patients undergoing RP by surgeons from 31 MUSIC practices, we identified 671 (28.7%) with high-risk features. aXRT was given to 29 patients (4.3%) at a median of 138 days (IQR 79-200 days) after RP. Use of aXRT varied by surgical pathology: 3/229 (1.3%) for pT2/PSMþ, 10/253 (4.0%) for pT3þ/PSM-, and 16/189 (8.5%) for pT3þ/PSMþ (p1⁄40.002). Higher pT stage was associated with aXRT (Fisher’s exact p<0.001), while age, race, PSA, grade, and PSM were not. After adjusting for patient characteristics, use of aXRT varied widely across practices (p<0.001), and was used in <5% of eligible patients at all but 7 sites (Figure). Of the 642 patients not receiving aXRT, 14 have received sXRT and 6 salvage androgen deprivation. Of the remaining 622 receiving no treatment to date, 35 (5.6%), 21 (3.4%), and 12 (1.9%) have reached PSA levels above 0.2, 0.5, and 1.0 ng/ml, respectively. CONCLUSIONS: In Michigan, utilization of aXRT, as well as early sXRT, is infrequent and variable across urology practices. Although the ideal use of aXRT in high-risk patients remains an area controversy, our findings suggest a need to understand the variability that exists in order to improve long-term oncologic outcomes in this subset of patients. Source of Funding: Blue Cross Blue Shield of Michigan