Histology significantly affects recurrence and survival following SBRT for early stage non-small cell lung cancer

Background: Contrary to prevailing notions of uniform efficacy regarding stereotactic body radiation therapy (SBRT) for early-stage non-small cell lung cancer (NSCLC), a recent report has indicated increased risk of local failure for squamous cell carcinoma (SCC). As those data have not been corroborated by other studies, we performed a multi-institutional analysis to evaluate the influence of histology on post SBRT outcomes. Materials and methods: Records from 152 consecutive patients who received SBRT for primary early-stage NSCLC at two academic medical centers were retrospectively assessed. Primary comparison was between SCC and adenocarcinoma. Patient outcomes including actuarial recurrences and overall survival were calculated using the Kaplan-Meier method. Univariable and multivariable logistic regression analyses addressed associated factors. Results: At a median follow-up of 44 months, patients with SCC had an increased risk of local, (hazard ratio (HR) (95% confidence interval (CI)): 1.69 (1.05-2.73), p = 0.032), regional (HR (95% CI): 2.03 (1.24-3.33), p = 0.005), and distant failure (HR (95% CI): 1.71 (1.06-2.77), p = 0.036). Median times to local (32 m vs 50m, p = 0.023), regional (26 m vs 50 m, p = 0.011), and distant (26 m vs 50 m, p = 0.024) failure were all significantly reduced in SCC histology. SCC histology was also independently associated with an increased risk for death (HR: 1.80 (1.10-2.94), p = 0.019) and had a 5-yr overall survival of 26%, versus 41% for adenocarcinoma (p = 0.016). Conclusions: This multi-institutional analysis corroborates that SCC histology is independently predictive for local, regional, and distant recurrence and worse overall survival. Future data are needed to determine if treatment paradigms should differ by histology for early stage NSCLC.