Stereotactic body radiation therapy with androgen deprivation therapy for unfavorable-risk prostate cancer.

Abstract

332 Background: Current ASTRO consensus guidelines do not support routine use of SBRT in higher risk PC. However, the NCCN permits selective use of SBRT with ADT for unfavorable intermediate (UIR) and high (HiR) risk PC in cases where conventional/moderately fractionated radiation therapy (EBRT) present medical or social hardship. How SBRT+ADT compares to EBRT+ADT in UIR and HiR men is unknown. Methods: Men >40 years old with localized PC treated with RT and concomitant ADT for curative intent between 2004-2015 were analyzed from the National Cancer Database. Patients treated with brachytherapy or who lacked ADT or risk stratification data were excluded. A total of 558 men treated with SBRT (5 fractions, ≥7 Gy/fraction) versus 40,797 men treated with moderate or conventional EBRT (dose ≥60 Gy with ≤3 Gy/fraction) were included. Patients were stratified by UIR and HiR using NCCN criteria. Kaplan Meier and Cox proportional hazards were used to compare overall survival (OS) between RT modality, adjusting for age, race, and comorbidity index. Results: With a median follow up of 62 months, there was no difference in 5-year OS between men treated with SBRT versus EBRT regardless of risk group (UIR: 87.2% SBRT versus 87.0% EBRT, p=.40; HiR: 80.4% SBRT versus 80.8% EBRT, p=.21). On multivariable analysis, there was no difference in risk of death for men treated with SBRT compared to EBRT (UIR: adjusted HR 1.09, 95% CI 0.68-1.74, p=.72; HiR: adjusted HR 0.93, 95% CI 0.76-1.14, p=.51). Conclusions: We found no difference in survival between SBRT+ADT and standard of care EBRT+ADT for UIR or HiR PC. Randomized trials of SBRT versus EBRT, with standard concomitant ADT, in these risks groups are needed. If prospectively validated, more widespread use of SBRT for higher risk PC may be warranted, especially in an era of cost-effective care.