Factors influencing noncompletion of radiotherapy among men with localized prostate cancer.

Abstract

199 Background: Treatment non-completion may occur with radiotherapy (RT), especially with protracted treatment courses such as RT for prostate cancer, and may affect the efficacy of RT. For men with localized prostate cancer managed with primary RT, we evaluated associations between rates of treatment non-completion and RT fractionation schedules. Methods: The National Cancer Database identified men diagnosed from 2004-2014 treated with primary RT. Patients receiving 180cGy/fraction (conventional), 200cGy/fraction (conventional), 250cGy/fraction (moderate hypofractionation), and 300cGy/fraction (moderate hypofractionation) were defined as having completed radiotherapy if they received ≥40 fractions, ≥37 fractions, ≥28 fractions, and ≥19 fractions, respectively. Stereotactic body radiotherapy (SBRT) was defined as 5-8 fractions of 600-800cGy/fraction. Odds ratios compared rates of treatment noncompletion, adjusting for various sociodemographic covariates. Propensity-adjusted multivariable Cox regression assessed the association between treatment completion and overall survival. Results: Of 93,079 patients, 90.5% (N = 84,260) received conventional fractionation, 2.3% (N = 2,181) received moderate hypofractionation, and 7.1% (N = 6,638) received SBRT. Rates of non-completion were 10.0% (N = 8,406) among patients who received conventional fractionation, 7.5% (N = 163) among patients who received moderate hypofractionation, and 1.7% (N = 115) among patients who received SBRT (OR versus conventional: 0.214, 95%CI 0.177-0.258, P < 0.001). The rate of non-completion among 15,417 African American patients was 11.8%, compared to 8.8% among 74,189 white patients (OR 1.39, 95%CI 1.31-1.47, P < 0.001). On subgroup analysis, the disparity in non-completion persisted for conventional fractionation (12.4% vs. 9.4%, OR 1.36, 95%CI 1.29-1.44, P < 0.001) and moderate hypofractionation (13.6% vs. 6.6%, OR 2.24, 95%CI 1.52-3.29, P < 0.001), but not for SBRT (2.0% vs. 1.6%, OR 1.25, 95%CI 0.76-2.06, P = 0.384). Non-completion was associated with worse survival on propensity-adjusted multivariate analysis (HR 1.37, 95%CI 1.31-1.43, P < 0.001). Conclusions: SBRT was associated with lower rates of RT non-completion among men with localized prostate cancer. African American race was associated with greater rates of treatment non-completion, although the disparity may be decreased among men receiving SBRT.