Post-Operative Radiation Therapy for Non-Small Cell Lung Cancer Patients With Higher Positive to Examined Lymph Node Ratio is Associated With Improved Overall Survival.

Purpose/Objective(s) A recent randomized controlled trial for post-operative radiation therapy (PORT) for non-small cell lung cancer (NSCLC) patients with N2 disease has suggested no clinical benefit. However, data regarding the possible correlation between lymph node disease burden and PORT outcomes is lacking. Materials/Methods The National Cancer Database (NCDB) NSCLC participant user file was used to identify patients who received upfront surgical resection and documented pathologic N2 disease. Patients not receiving chemotherapy were excluded. A positive to examined lymph node (PEN) ratio was calculated by dividing the number of positive lymph nodes by the number of examined lymph nodes (range 0 – 1.0). The PEN ratio was then divided into quartiles to compare overall survival (OS) with and without PORT. Cox proportional hazards modeling (CPHM) was used to assess the association between OS and PORT status by quartile group. Results From 2004 to 2017, 22,354 NSCLC patients received upfront surgery and were found to have pathologic N2 disease. The median number of lymph nodes examined was 11 (Interquartile Range 6, 16). Median OS decreased with increasing PEN ratio: 0-0.16: 58 months, 0.17-0.30: 49 months, 0.31-0.50: 37 months, 0.51-1.0: 29 months, P Conclusion While a recent prospective clinical trial demonstrated no clinical benefit to PORT in the setting of N2 disease, this analysis shows that there may be a select population of patients that may benefit as the ratio of positive to examined lymph nodes increases. Secondary analyses in prospective trials may help delineate the role of the PEN ratio in treatment selection.