Survival impact of unexpected N2 in stage IIIB/N2 non-small cell lung cancer patients

Background We investigated the effect of unexpected N2 on survival in stage IIIB/N2 cases. Methods We retrospectively analyzed 1803 non-small cell lung cancer patients between 2010 and 2016. There were 89 patients (4.9%) with unexpected N2 (pathological (p) IIIB/N2 group), whereas 49 patients (2.7%) with cN2 (clinical (c) IIIB/N2 group). Although pIIIB/N2 group underwent surgery followed by adjuvant therapy, the cIIIB/N2 group of patients had multimodality treatment including induction chemotherapy +/- radiotherapy followed by surgery. Results The five-year overall survival (OS) for all patients was 36.0% [median survival time (MST) 27.9 months], and disease-free survival (DFS) was 28.9% (MST, 18.2 months). The OS was 39.6% (MST: 34.4 months) and the median DFS time was 31.1% (Median: 23.1 months) in the pIIIB/N2 group, whereas it was 29.2% (MST: 23.0 months) for OS and 22% (median: 12.4 months) for DFS in the cIIIB/N2 group. There were no significant OS and DFS differences between the pIIIB/N2 group and the cIIIB/N2 group (p = 0.124 and p = 0.168, respectively). Conclusions In stage IIIB/N2 cases, the fact that N2 could not be detected preoperatively with minimally invasive or invasive methods and was detected in the pathological examination after surgery does not provide a survival advantage.