Long-term outcomes of single and five fraction schedules of stereotactic body radiation therapy for early-stage central or peripheral NSCLC: Neither fractionation nor location matter?

Abstract

8538 Background: Due to concerns with toxicity, treatment of early-stage non-small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT) often involves different fractionation schemes for peripheral and centrally located tumors. There is a paucity of long-term SBRT survival outcomes comparing peripheral versus central NSCLC. Methods: This is a single-institution observational cohort study of patients diagnosed with early-stage NSCLC (T1-2N0M0) who underwent 27 Gy in 1 fraction or 50 Gy in 5 fractions with heterogeneity correction at Roswell Park Comprehensive Cancer Center between September 2008 to December 2018. All patients treated with single-fraction SBRT had peripheral NSCLC and those treated with five-fraction SBRT had central NSCLC. Clinically relevant variables including age, gender, race, Karnofsky Performance Status (KPS), histology (adenocarcinoma, squamous cell carcinoma, NSCLC not otherwise specified), T stage, smoking status, tumor location, and the year of SBRT delivery were obtained retrospectively. Cox multivariable analysis (MVA), Kaplan-Meier plot, and log-rank test were performed to evaluate progression-free survival (PFS) and overall survival (OS). Fine-Gray competing risk MVA was performed to evaluate local failure (LF), nodal failure (NF), and distant failure (DF) with death as a competing event. To reduce selection bias, propensity score matching was performed between single- versus five-fraction SBRT cohorts. Results: A total of 265 patients (142 female [53.6%]; median age 77 years) met our criteria. There were 74 (27.9%) and 191 (72.1%) patients with central tumors treated with five-fraction SBRT and peripheral tumors treated with single-fraction SBRT, respectively. On Cox MVA, there was no statistically significant difference in OS (peripheral vs central tumors: adjusted hazards ratio [aHR] 1.04, 95% confidence interval [CI] 0.74-1.46, p=0.81) and PFS (peripheral vs central tumors: aHR 1.05, 95% CI 0.76-1.45, p=0.77). On Fine-Gray competing risk MVA comparing peripheral vs. central tumors, there was no statistically significant difference in LF, NF, and DF. After propensity score matching, 68 matched pairs were identified for peripheral vs. central tumors with similar results. Conclusions: Among patients with early-stage NSCLC treated with SBRT central versus peripheral location was associated with similar long-term survival and tumor recurrence outcomes.