Role of Adjuvant Radiation in pN2 Non-Small Cell Lung Cancer (NSCLC) Patients

Abstract

Past studies have shown mixed results of postoperative radiation (PORT) for pN2 NSCLC patients and the recent LungART trial has shown no disease free survival or overall survival (OS) benefits with PORT for pN2 NSCLC patients. High lymph node ratio (LNR = number of positive lymph nodes in the resected specimen/number of total lymph nodes resected) has been shown to correlate with worse outcomes. We hypothesize that PORT can improve survival outcomes in pN2 NSCLC patients with high LNR.The National Cancer Database was queried for cases of NSCLC from 2004-2016. Patients without neoadjuvant treatment, with at least a lobectomy with resection of at least 10 lymph nodes, with pN2 disease, with histology of squamous cell carcinoma, adenocarcinoma, adenosquamous carcinoma and large cell carcinoma were included. Exclusion criteria were neoadjuvant therapy, lack of pathological confirmation or lack of information about chemotherapy and metastatic disease. For patients with PORT, RT was directed to thorax with dose≥30Gy. Log-rank test and Cox proportional hazards models were used to compare survival adjusted for age, sex, CCI, pT, grade, chemotherapy, LNR, and PORT. Predictors for overall survival (OS) were identified.Among 10272 patients, 6266 (61%) did not have PORT, and 4006 (39%) had PORT. Median follow up was over 5 years. PORT was given to 51.3% and 37.7% patients with non-R0 and R0 resection, respectively (P < 0.001). PORT was given to 48.4% and 9.91% of patients with and without adjuvant chemotherapy, respectively (P < 0.001). The average LNR for patients with and without PORT were 0.33 and 0.29 (P < 0.001), respectively. In multivariate analysis (MVA) of patients with R0 resection, predictors of OS were listed in Table 1. PORT was not associated with better OS (HR, 1.04, P = 0.63) for patients with LNR of 1-15%. However, PORT was associated with better survival in patients with higher LNRs (HR, 0.90, P = 0.23 for LNR of 15-29% and HR, 0.82, P = 0.01 for LNR ≥ 30%). In MVA of patients with non-R0 resection, PORT was associated with better survival (HR, 0.56, P = 0.01).High LNR after R0 surgery in pN2 NSCLC patients portends worse survival. PORT is associated with better survival for pN2 NSCLC patients after R0 resection with high LNR after accounting for multiple confounders including adjuvant chemotherapy. PORT is also associated with better survival in pN2 NSCLC patients after R1 or R2 surgery.