Comparison of Single- and Three-Fraction Schedules of Stereotactic Body Radiation Therapy for Peripheral Early-Stage Non–small Cell Lung Cancer: A Single Institution Experience

Abstract

Stereotactic Body Radiation Therapy (SBRT) is an alternative treatment option for medically inoperable patients with early-stage non-small cell lung cancer (NSCLC). The optimal dose and fractionation for NSCLC remain unclear. The aim of this study is to compare the clinical outcome of patients with early-stage NSCLC who underwent either single-fraction (SF) or three-fraction (TF) SBRT at a single institution over 8 years. Between February 2007 and November 2015, patients with peripherally located early-stage NSCLC who underwent SBRT were included in this study. Data were retrospectively reviewed and collected in an institutional review board-approved database. Overall survival and progression-free survival were analyzed using the Kaplan-Meier method and log-rank tests. Local, nodal, and distant failures were assessed using the competing risks method and Gray’s tests. Potential prognostic factors were examined using Cox regression. Toxicity was evaluated using the Common Terminology Criteria for Adverse Events (version 4.0). R software (version 3.3.2) was used for statistical analyses. Of 158 patients with 162 total lung tumors, 68 lesions received 30-34 Gy (median 30 Gy) in 1 fraction, while the remaining 94 lesions received 48-60 Gy (median 60 Gy) in 3 fractions. After a median follow-up of 17.1 months for SF-SBRT and 19.1 months for TF-SBRT groups (p=0.54), there was no statistically significant difference in overall survival (p=0.93), local failure (p=0.96), nodal failure (p=0.82), and distant failure (p=0.65) at 18 months. Among the incidences of nodal or distant failure (n=21 for SF-SBRT, n=28 for TF-SBRT), median time to failure was 11.5 months and 10.2 months for the SF- and TF-SBRT groups, respectively (p=0.45). No grade 3+ toxicity in the SF-SBRT group was reported, while only a single case of grade 3 pulmonary embolism in the TF-SBRT group was reported 10 months after the SBRT. A large tumor size was associated with poor overall survival (HR=1.22, p=0.045), and male gender was associated with a higher risk for nodal (HR=2.81, p=0.013) and distant failures (HR=2.00, p=0.036). The SF- and TF-SBRT groups showed no significant difference in overall survival, local failure, nodal failure, distant failure, and the onset of nodal or distant failure. Both SF-SBRT and TF-SBRT regimens were well tolerated. Small tumor size was a favorable prognostic factor for overall survival, whereas male gender was an adverse prognostic factor for nodal and distant failures. The similarity in clinical outcomes between these two schedules is notable since patients with worse prognosis or performance status tend to receive SF-SBRT.