Patients with ypN2 Non-Small Cell Lung Cancer after Neoadjuvant Chemotherapy Followed By Surgery Can Benefit from Postoperative Radiotherapy- a Retrospective Study of Surveillance, Epidemiology, and End Results Database

Abstract

Neoadjuvant chemotherapy followed by surgery (NCS) is a common therapy pattern of resectable non-small cell lung cancer (NSCLC). However, for patients with ypN2 disease after aforementioned treatment, there is no evidence that postoperative radiotherapy (PORT) should be adopted or not. Our study is to evaluate the effect of PORT on survival of patients with ypN2 NSCLC after NCS from Surveillance, Epidemiology, and End Results (SEER) database. We filtrated data from SEER database by the inclusion criteria of patients with NSCLC diagnosed at 2004-2015, treated with NCS, and with ypN2 disease (2004-2009 AJCC 6th, 2010-2015 AJCC 7th). We excluded patients with unclear basic information (such as sex, histology or cause of death), multiple primary malignant tumor and M1 disease. All data were analyzed using statistical analysis software and propensity-score matched analysis was used to match the base-line characteristics between PORT group and non-PORT group. Kaplan-Meier method was used to estimate overall survival (OS) and cancer specific survival (CSS). Univariable and multivariable Cox proportional hazards models were adopted to estimate hazard ratios (HR) of predictors of survival. From 331 patients receiving NCS, 215 meeting the criteria were included in the final analysis. There were 112 patients (52.1%) with PORT. The baseline characteristics of majority were as follows: age≤65 (55.3%), white (82.3%), female (54.4%), grade 3-4 (63.3%), adenocarcinoma (60.0%), tumor size of 3-5 cm (38.6%), lobectomy (80.0%) and positive lymph nodes≥4 (51.2%). There were 200 patients remained after the prosperity score matching between the PORT group and the non-PORT group, with 100 cases in each. The median OS of the two groups were 36 months vs 26 months and 5-year OS rates were 36.2% vs 20.3%, respectively (P=0.011). The median CSS were 36 months versus 27 months and 5-year CSS were 38.5% vs 21.1%, respectively (P=0.010). Univariable analysis showed that only PORT significantly improved OS (HR=0.648, P=0.013) and CSS (HR=0.639, P=0.012). Multivariable analysis confirmed that PORT was the only significant predictor of OS (HR=0.615, P=0.011) and CSS (HR=0.614, P=0.013). For patients with ypN2 NSCLC after NCS, PORT can significantly improve the OS and CSS . However, the result needs to be clarified by prospective randomized clinical trials.