Invasive nodal evaluation prior to stereotactic ablative radiation for non-small cell lung cancer

Introduction: Invasive nodal evaluation (INE) is used to improve staging for early stage non-small cell lung cancer (NSCLC), including when stereotactic ablative radiation (SABR) is used. Consensus guidelines from the NCCN recommend performing INE for patients with T2N0 tumors and considering INE for those with T1N0 tumors. We reasoned that if INE results in significant stage migration in the form of substantially fewer patients with occult nodal involvement, then patients treated with SABR who do not undergo INE should have worse overall survival (OS). Methods: Patients diagnosed 2004–2014 with stage T1–2N0M0 NSCLC and treated with SABR were identified from the National Cancer Database. Factors associated with INE were determined using mixed effects logistic regression. We tested for an association between INE and OS for patients diagnosed 2004–2013 using mixed effects proportional hazards regression methods. Results: 24,603 SABR patients were identified. 6% of the 19,322 patients with T1 tumors and 9% of the 5281 patients with T2 tumors had INE. Median OS was 2.8 years for the no-INE group and 2.7 years for the INE group (log-rank P = 0.69). No significant association was observed between the use of INE and OS in the univariate analysis (HR 1.02, 95% CI 0.94–1.11) or the multivariate analysis (HR 0.94, 95% CI 0.86–1.02). These findings were confirmed using propensity score matched and instrumental variable analysis. On subgroup analysis, INE was associated with a non-significant trend for improved OS in patients with T2 tumors (HR 0.87, 95% CI 0.76–1.00) but not T1 tumors (HR 0.98, 95% CI 0.88–1.09). Conclusions: Despite current NCCN recommendations, the rate of INE was low for patients with stage T1 or T2 tumors. While omitting INE represents a compromise in the completeness of nodal evaluation, we found that it was not associated with a detriment in overall survival.