Survival Outcomes After Radiation Therapy for Stage III Non–Small-Cell Lung Cancer After Adoption of Computed Tomography–Based Simulation

Abstract

Purpose Technical studies suggest that computed tomography (CT) –based simulation improves the therapeutic ratio for thoracic radiation therapy (TRT), although few studies have evaluated its use or impact on outcomes. Methods We used the Surveillance, Epidemiology and End Results (SEER) –Medicare linked data to identify CT-based simulation for TRT among Medicare beneficiaries diagnosed with stage III non–small-cell lung cancer (NSCLC) between 2000 and 2005. Demographic and clinical factors associated with use of CT simulation were identified, and the impact of CT simulation on survival was analyzed by using Cox models and propensity score analysis. Results The proportion of patients treated with TRT who had CT simulation increased from 2.4% in 1994 to 34.0% in 2000 to 77.6% in 2005. Of the 5,540 patients treated with TRT from 2000 to 2005, 60.1% had CT simulation. Geographic variation was seen in rates of CT simulation, with lower rates in rural areas and in the South and West compared with those in the Northeast and Midwest. Patients treated with chemotherapy were more likely to have CT simulation (65.2% v 51.2%; adjusted odds ratio, 1.67; 95% CI, 1.48 to 1.88; P < .01), although there was no significant association between use of surgery and CT simulation. Controlling for demographic and clinical characteristics, CT simulation was associated with lower risk of death (adjusted hazard ratio, 0.77; 95% CI, 0.73 to 0.82; P < .01) compared with conventional simulation. Conclusion CT-based simulation has been widely, although not uniformly, adopted for the treatment of stage III NSCLC and is associated with higher survival among patients receiving TRT.