Survival Patterns for Patients with Resected N2 Non–Small Cell Lung Cancer and Postoperative Radiotherapy: A Prognostic Scoring Model and Heat Map Approach

Introduction: The positive-to-resected lymph node ratio (LNR) predicts survival in many cancers, but little information is available on its value for patients with N2 NSCLC who receive postoperative radiotherapy (PORT) after resection. We tested the applicability of prognostic scoring models and heat mapping to predict overall survival (OS) and cancer-specific survival (CSS) in patients with resected N2 NSCLC and PORT. Methods: Our test cohort comprised patients identified from the Surveillance, Epidemiology, and End Results database with N2 NSCLC who received resection and PORT in 2000–2014. Prognostic scoring models were developed to predict OS and CSS using Cox regression; heat maps were constructed with corresponding survival probabilities. Recursive partitioning analysis was applied to the Surveillance, Epidemiology, and End Results data to identify the optimal LNR cutoff point. Models and cutoff points were further tested in 183 similar patients treated at The University of Texas M. D. Anderson Cancer Center in 2000–2015. Results: Multivariate analyses revealed that low LNR independently predicted better OS and CSS in patients with resected N2 NSCLC who received PORT. Conclusions: LNR can be used to predict survival of patients with resected N2 NSCLC followed by PORT. This approach, which to our knowledge is the first application of heat mapping of positive and negative lymph nodes, was effective in estimating 3-, 5-, and 10-year OS probabilities.