Stereotactic ablative radiotherapy (SABR) in early stage non-small cell lung cancer: Comparing survival outcomes in adenocarcinoma and squamous cell carcinoma

Purpose: Recent retrospective studies have demonstrated mixed results regarding the histologic association of squamous cell carcinoma (SCC) with reduced overall survival in patients with early-stage non-small cell lung cancer (ES-NSCLC) treated with stereotactic ablative radiotherapy (SABR). Methods: We queried the National Cancer Database (NCDB) for ES-NSCLC (T1-2N0, Stage I-IIA) patients with SCC or adenocarcinoma (ADC) treated with SABR. Univariable and multivariable analyses identified characteristics predictive of overall survival. Cox proportional hazard ratios with propensity adjustment were used to mitigate indication bias between the two histologic arms. Results: Ultimately 15,110 ES-NSCLC patients with either ADC (n = 8,924) or SCC (n = 6,186) were eligible for analysis. Univariable analysis demonstrated a median overall survival of 44 months and 33 months (p < 0.0001) and 5-year overall survival of 36% and 24% (p < 0.0001) in patients diagnosed with ADC and SCC, respectively. SCC histology, remained an independent predictor of worse survival on propensity score matched multivariable comparison (p < 0.0001). Patients with SCC were more likely to have T2 lesions and poorly differentiated grade. Females, African American race, T1 lesions, and age < 75 years were also associated with improved survival. Conclusion SCC histology was an independent prognosticator of worse survival in patients with ES-NSCLC treated with SABR, thus corroborating the results of previous studies. Randomized, prospective studies are needed to further validate these findings.