Factors influencing non-completion of radiotherapy among men with localized prostate cancer.

INTRODUCTION 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 or 200cGy/fraction were defined as having completed radiotherapy if they received ≥41 fractions of 180cGy/fraction or ≥37 fractions of 200cGy/fraction respectively. Stereotactic body radiotherapy (SBRT) was defined as 5-8 fractions of 600-800cGy/fraction. Odds ratios compared rates of treatment noncompletion, adjusting for sociodemographic covariates. Propensity-adjusted multivariable Cox regression assessed the association between treatment completion and overall survival. RESULTS Of 157,657 patients, 95.7% (N=150,847) received conventional fractionation and 4.3% (N=6,810) received SBRT. Rates of non-completion were 12.5% (N= 18,803) among patients who received conventional fractionation and 1.9% (N=131) among patients who received SBRT (OR versus conventional: 0.21, 95%CI 0.18-0.26, P<0.001).The rate of non-completion among 25,727 African American patients was 12.8%, compared to 11.8% among 126,199 white patients (OR 1.14, 95%CI 1.09-1.19, P<0.001). On subgroup analysis, the disparity persisted in non-completion persisted for conventional fractionation (13.2% vs. 12.3%, OR 1.09, 95%CI 1.05-1.13, P<0.001), but not for SBRT (2.2% vs. 1.8%, OR 1.26, 95%CI 0.79-2.00, P=0.34). Non-completion was associated with worse survival on propensity-adjusted multivariable analysis (HR 1.25, 95%CI 1.22-1.29, 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.