A Comparison of Radiation Techniques in Patients Treated with Concurrent Chemoradiation for Stage III Non-Small Cell Lung Cancer

Abstract

The standard of care in the management of stage III non-small cell lung cancer (NSCLC) is concurrent chemoradiation. Recently, newer more conformal techniques with intensity modulated radiation therapy (IMRT) and volumetric arc therapy (VMAT) are being used. It is unclear whether a more conformal technique ultimately improves survival in patients with stage III lung cancer. We looked at population-based data to examine this question. A retrospective cohort of stage III NSCLC patients treated with concurrent chemoradiation with curative intent between 2009-2014 in Ontario were identified from the ICES (Institute of Clinical Evaluative Sciences) database. Patients were excluded if they had surgery, sequential chemoradiation or radiation alone. Outcomes were compared for patients treated with 3D conformal radiation (3D-CRT), IMRT and VMAT. The primary endpoint was overall survival (OS), calculated using the Kaplan-Meier method and compared using log-rank test. Cox regression was used to investigate effect of radiation type on OS. A minimal clinically important difference (MCID) was set at ≥15%. Between 2009-2014, a total of 2507 patients were treated with 3D-CRT (N=925), IMRT (N=1227) or VMAT (N=355). The rate of 3D-CRT use declined (from 65% in 2009 to 14% in 2014) while the rates of IMRT (35% to 53%) and VMAT (0% to 33%) use concurrently increased. Median survival in months was 22.7 [95% CI 21.0-24.4] for 3D-CRT, 20.8 [95% CI 19.6-22.2] for IMRT and 24.3 [95% CI 20.6-27.9] for VMAT (p=0.041 for all 3 groups, and p=0.046 for 3D CRT vs IMRT alone). The 5 year OS was 22.1% [95% CI 19.2-25.1] for 3D-CRT vs 18.1% [95% CI 15.4-20.9] for IMRT (p=0.046). Prognostic factors for survival on multivariable analysis included male sex [HR 1.29, 95% CI 1.18-1.42, p <0.001], income quintile [HR 0.95, 95% CI 0.92-0.99, p = 0.004], age [HR 1.03, 95% CI 1.00-1.06, p = 0.04], and radiation type [IMRT HR=1.12, 95% CI 1.01-1.24; VMAT HR=0.91, 95% CI 0.76-1.09, p=0.012]. There is increased uptake of more conformal techniques over time amongst stage III NSCLC patients. Although a statistically significant difference in OS was observed, this was likely driven by unmeasured patient selection effects. Absolute differences were modest and did not meet clinical significance.