Log odds of positive lymph nodes is a robust predictor of survival and benefits from postoperative radiotherapy in stage IIIA-N2 resected non-small cell lung cancer.

Background: The significance of postoperative adjuvant radiotherapy (PORT) on the survival of resected IIIA-N2 non-small cell lung cancer (NSCLC) remains controversial. Here, we aimed to determine the predictive value of the three nodal classifications which might aid in PORT decision-making.

Methods: A total of 4797 patients with stage IIIA-N2 resected NSCLC were identified in the Surveillance, Epidemiology and End Results (SEER) database and were grouped by whether PORT was administered. Survival analysis was used to identify the patient groups who can benefit from PORT. Multivariate analysis was performed to confirm the independent risk factors for lung cancer-specific survival (LCSS) and overall survival (OS). A validation cohort of 1184 patients from three medical centers in China were also included.

Results: PORT was not associated with better LCSS and OS in the entire cohort after propensity score matching (PSM). However, in the subgroups of positive lymph nodes 4 (PLN4), lymph node ratio 4 (LNR4), and log odds of positive lymph nodes 4 (LODDS4), PORT exhibited its role in improving LCSS (p < 0.05). Although the three nodal classifications were all identified as independent predictors of LCSS and OS, LODDS classification had the best discriminatory ability and prognostic accuracy for stage IIIA-N2 patients. Similar results were also obtained in the validation cohort.

Conclusions: The LODDS classification not only exhibited the best prognostic performance in predicting LCSS and OS in stage IIIA-N2 disease, but also could help tailor individualized PORT.