The impact of histology in the outcomes of patients with early-stage non-small cell lung cancer (NSCLC) treated with stereotactic body radiation therapy (SBRT) and adjuvant chemotherapy

Introduction: Stereotactic body radiation therapy (SBRT) is the standard of care treatment for nonsurgical patients with early-stage non-small cell lung cancer (NSCLC). A recent report has indicated an improvement in overall survival (OS) with adjuvant chemotherapy in patients with tumors ≥ 4 cm treated with SBRT. We present a retrospective study evaluating the impact of histology in patients treated with SBRT and adjuvant chemotherapy. Materials and Methods: Patients (≥18 years) diagnosed with clinical stages I-II NSCLC from 2004 to 2013 were identified using the National Cancer Database (n = 12,055). 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. We performed subgroup analysis for the three main NSCLC histologies (i.e., adenocarcinoma, squamous cell carcinoma (SCC), and large cell). Results: In patients with adenocarcinoma, SCC and, large cell carcinoma; adjuvant chemotherapy was associated with worse OS in tumors < 4 cm (P<.0001, P<.0099, and P=.0082, respectively). In patients with adenocarcinoma and tumor ≥ 4 cm, adjuvant chemotherapy was not associated with improved OS (P=.262); however, in patients with SCC and large cell, adjuvant chemotherapy improved OS (P<.0001, and P=.0129, respectively). Conclusion: In patients with NSCLC ≥ 4 cm treated with SBRT, adjuvant chemotherapy was associated with improved OS in patients with SCC and large cell histologies.