Role of Adjuvant Radiation in pN1 Non-Small Cell Lung Cancer (NSCLC) Patients

Abstract

Previous studies have shown a detrimental effect of postoperative radiation (PORT) in pN1 NSCLC patients after R0 surgery. 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 pN1 NSCLC patients with high LNR after R0 surgery.The National Cancer Database was queried for cases of lung cancer from 2004-2016. Patients without neoadjuvant treatment, with at least a lobectomy with resection of at least 10 lymph nodes, with pN1 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 13742 patients, 12542 (91.3%) did not have PORT, and 1200 (8.7%) had PORT. Median follow up was over 5 years. For years of 2004-2010 and 2011-2016, PORT was given to 8% (413 out of 5132) and 5.5% (423 out of 7622) of patients after R0 resection, respectively. PORT was given to 36.8% and 6.55% patients with non-R0 and R0 resection, respectively (P < 0.001). PORT was given to 11.6% and 3.37% of patients with and without adjuvant chemotherapy, respectively (P < 0.001). The average LNR for patients with and without PORT were 0.2 and 0.14 (P < 0.001), respectively. In multivariate analysis (MVA) of patients with R0 resection, predictors of OS were listed in Table 1. In patients with intermediate LNR (15-29%), PORT was marginally correlated with better OS (HR, 0.80, P = 0.07). In patients with high LNR (≥30%), PORT was correlated with better OS (HR, 0.80, P = 0.047). In MVA of patients with non-R0 resection, high LNR was associated with worse OS (HR, 1.35 and 1.66 for LNR of 15-29% and ≥30%, respectively). In patients with intermediate (15-29%) and high (≥30%) LNR, PORT was numerically correlated with better OS (HR, 0.89 and 0.77 respectively, P non-significant).For pN1 NSCLC patients after R0 resection, use of PORT is decreasing. High LNR after R0 surgery in pN1 NSCLC patients portends worse survival. PORT does not benefit pN1 NSCLC patients with low LNR after R0 surgery, but it is associated with better survival for patients with high LNR after accounting for multiple confounders including adjuvant chemotherapy.