Adjuvant radiation therapy improves survival in stage IIIA (N2) non-small cell lung cancer with persistent N2 disease after neoadjuvant chemotherapy

Abstract

ObjectivesRole of adjuvant radiation therapy in stage III (N2) non-small cell lung cancer has been controversial over the decades. Recent large, randomized trials have demonstrated that adjuvant radiation did not improve overall survival or disease-free survival; however, the trials either excluded or enrolled very few cases that have undergone neoadjuvant chemotherapy. Role of adjuvant radiation after neoadjuvant chemotherapy remains unclear. Whether the use of adjuvant radiation is associated with improved overall survival in those who have received neoadjuvant chemotherapy, especially in a subgroup of patients with persistent N2, is unknown. Materials and methodsPatients with clinical stage III (N2) non-small cell lung cancer diagnosed from 2004 through 2017 were queried to National Cancer Database. Eligibility criteria included completely resected (R0), pathological diagnosis, neoadjuvant multi-agent chemotherapy, information regarding post-surgical N2 status (persistent versus downstaged to pN0-1), adjuvant radiation (45 Gy+ versus none), and American Joint Commission on Cancer staging version (6th versus 7th). Those who have received neoadjuvant radiation with any dose or adjuvant radiation with less than 45 Gy total dose were excluded. Kaplan-Meier and log-rank tests were used for survival analyses. Propensity-score matching analysis was used for validation. All statistical analyses were two-sided, and p < 0.05 was required for statistical significance. ResultsA total of 1,855 patients met the eligibility criteria for analysis. In the overall cohort, there was a significant difference in overall survival between persistent N2 (Cohort P: N = 854, median survival 50.7 months) and downstaged N (Cohort D: N = 1,001, median survival 82.7 months). The use of adjuvant radiation showed a non-significant detrimental effect in overall survival in the overall and Cohort D (univariate p-values 0.27 and 0.077, respectively); however, both univariate and multivariate analyses demonstrated a significant improvement in overall survival in Cohort P (p = 0.004 and 0.028, respectively). These findings are also verified by propensity-score matching analysis (p = 0.0347). ConclusionsThis large-scale retrospective analysis suggests that adjuvant radiation may still have a role in persistent N2 disease after neoadjuvant chemotherapy. Further investigations are warranted.