EP1.17-21 Early Stage NSCLC (ES-NSCLC) 5-Fraction Stereotactic Body Radiation Therapy (SBRT) 3-Year Patterns of Failure

Abstract

SBRT is an effective treatment for ES-NSCLC. Five fraction approaches have been advocated to limit treatment induced toxicity. In this report, we evaluate 3-year patterns of failure for an institutional 5 fraction protocol. Medically inoperable patients were treated with frameless robotic SBRT. PET/CT was completed for staging and at 6 month follow up intervals. A tumor was considered central if it was located within 2 cm of the proximal bronchial tree (PBT). From December 2010 to December 2015, 50 patients with biopsy proven ES-NSCLC (stage I - 31; stage II – 19) with median age of 75 were treated to 50 Gy in 5 fractions. Thirty-nine tumors were peripheral and 11 were centrally located. The majority of peripheral tumors were adenocarcinoma (73%) and the majority of central tumors were squamous cell carcinoma (73%). At median follow up of 36 months, local control, regional control, distant metastasis free survival (DMFS) and overall survival (OS) were 88%, 92%, 83% and 52% for all patients. Local control for peripheral tumors was significantly better than central tumors (94% vs. 60% p-value=0.018). Squamous tumors constituted 60% of local failures despite making up 40% of the entire cohort. Conversely, 12% of peripheral adenocarcinoma failed regionally comprising the only regional failures in this series. DMFS (88% vs. 81% p-value=0.445) and OS (46% vs. 54% P=0.421) were not different for central and peripheral tumors. Acceptable outcomes are achievable for central and peripheral inoperable ES-NSCLC patients treated with 5-fraction SBRT alone. However, future trials should consider the addition of systemic therapy to reduce the risk of locoregional and distant failures.