Central versus Peripheral Tumor Location Influence on Survival, Local Control, and Toxicity Following Stereotactic Body Radiotherapy for Primary Non-Small-Cell Lung Cancer

Introduction: Stereotactic body radiotherapy (SBRT) has been increasingly utilized for medically inoperable early stage non-small-cell lung cancer. However, a lower biological equivalent dose (BED) is often used for central tumors given toxicity concerns, potentially leading to decreased local control (LC). We compared survival, LC, and toxicity outcomes for SBRT patients with centrally versus peripherally located tumors. Methods: We included patients with primary cT1-2N0M0 non-small-cell lung cancer treated with SBRT at our institution from September 2007 to August 2013 with follow-up through August 2014. Central tumor location was defined as within 2 cm of the proximal bronchial tree, heart, great vessels, trachea, or other mediastinal structures. Kaplan-Meier analysis and multivariable Cox regression modeling were used for overall survival (OS) and LC, and the chi(2) test and multivariable logistic regression modeling were used for toxicity. Results: We included 251 patients (111 central, 140 peripheral) with median follow-up of 31.2 months. Patients with central tumors were more likely to be older (mean 75.8 versus 73.5 years; p = 0.04), have larger tumors (mean 2.5 cm versus 1.9 cm; p < 0.001), and be treated with a lower BED (mean 120.2 Gy versus 143.5 Gy; p < 0.001). Multivariable analysis revealed that tumor location was not associated with worse OS, LC, or toxicity. Patients with central tumors were less likely to have acute grade greater than or equal to three toxicity than those with peripheral tumors (odds ratio: 0.24; p = 0.02). Conclusions: Central tumor location did not predict for inferior OS, LC, or toxicity following SBRT when a lower mean BED was utilized.