Predictors Of Radiation Therapy (Rt) Use Among Medicare Patients With Metastatic Non-Small Cell Lung Cancer (Nsclc)

124 Background: Palliative RT can improve quality of life, but also incurs time and financial costs. We evaluated factors associated with use and intensity of palliative RT for metastatic NSCLC.Using SEER-Medicare data, we identified patients diagnosed with pathologically confirmed stage IV NSCLC from 2004-2011. Receipt of RT and total fractions in the first RT course was collected. Univariable and multivariable logistic regression were used to identify factors associated with RT receipt and higher intensity RT ( > 10 fractions). Models were adjusted for clustering at the county level.Among 53,371 patients with stage IV NSCLC, 39% (20,937) received palliative RT. Among patients receiving RT, 48% (10,048) received > 10 fractions and only 3.5% (724) received single fraction RT. On multivariable analysis, factors associated with greater RT use included younger age group (overall p < .01), lower Charlson comorbidity score (overall p < .01), female gender (OR 1.1, p < .01), married status (OR 1.1, p < .01), South (OR 1.0) and Midwest (OR 1.1) SEER region vs. Northeast (ref) or West (OR 0.9) (overall p < .01), higher radiation oncologist density tertile (OR 1.1, overall p = .02), hospice use (OR 1.47, p < .01), and chemotherapy use (OR 3.61, p < .01). Among patients treated with RT, predictors for > 10 fractions were older age group (overall p = .03), no hospice use (OR 1.1, p < .01), chemotherapy use (OR 1.9, p < .01) and freestanding vs. hospital-based RT facility (OR 1.66, p < .01).A combination of patient, treatment, and health service factors influenced whether a patient received palliative RT. In contrast, most patient factors (except age) did not influence the decision to treat with higher intensity radiation. The receipt of chemotherapy and treatment at a freestanding RT facility were highly predictive for extended RT fractionation, which may have been partially driven by higher reimbursement rates to freestanding facilities during this period.