Adjuvant Systemic Therapy in Patients With Early-Stage NSCLC Treated With Stereotactic Body Radiation Therapy

Introduction: Stereotactic body radiation therapy (SBRT) is commonly used to treat nonsurgical patients with early-stage NSCLC. There are no prospective data on the role of adjuvant chemotherapy in this setting. Methods: Patients (≥18 years) diagnosed with clinical stages I-II NSCLC from 2004 to 2013 were identified using the National Cancer Database (n = 11,836). The Kaplan-Meier method was used to estimate overall survival (OS) distributions and the log-rank test was used to compare distributions by treatment strategy. Clinical stages I and II were subdivided according to the TNM staging and log-rank tests was used to compare survival distributions by treatment strategy within each subgroup. Results: In patients with T2bN0, median OS in the SBRT alone and SBRT plus adjuvant chemotherapy groups were 16.5 months versus 24.2 months, respectively (95% confidence interval [CI]: 14.1–20.1 months and 18.8–33.3 months, respectively; p <.001); whereas for T3N0, median OS times were 13 months and 20.1 months, respectively (95% CI: 11.7–14.5 mohths and 17.7–21.9 months, respectively; p <.001). For tumors 4 cm or larger and node-negative disease, median OS was 15.9 months in the SBRT-alone group, and 19 months in the SBRT-plus-chemotherapy group (95% CI: 15.1–16.8 months and 17.9–20.8 months, respectively; p <.001). For patients with tumors less than 4 cm and node-negative disease, the median OS was 28.5 months in the SBRT-alone group and 24.3 months in the SBRT-plus-chemotherapy group (95% CI: 27.4–29.4 months and 22.8–26.1 months, respectively; p <.001). Conclusions: SBRT followed by adjuvant chemotherapy was associated with improved OS in comparison with SBRT alone in patients with T greater than or equal to 4 cm, similar to that seen after surgery.