Prognostic and predictive value of the novel classification of lung adenocarcinoma in patients with stage IB

Controversy remains exist for the effect of adjuvant chemotherapy (ACT) among stage IB lung adenocarcinoma patients. This study aimed to investigate the predictive value of the current lung adenocarcinoma classification system on benefit of ACT among patients with stage IB lung adenocarcinoma. A total of 928 pathological stage IB invasive adenocarcinoma patients with R0 resection were included in this study. Based on the predominant growth pattern present in the tumor, invasive adenocarcinomas with mixed histologic components were classified into five subtypes: lepidic (LEP), acinar (ACN), papillary (PAP), micropapillary (MIP) and solid (SOL). These five histologic subtypes were collapsed into three groups (LEP, ACN/PAP and SOL/MIP). Disease-free survival (DFS) and overall survival (OS) were analyzed to evaluate benefit from ACT in patients with different histologic patterns using the Kaplan-Meier approach and multivariable Cox models. For all stage IB invasive adenocarcinoma patients, SOL/MIP subgroup presented the worst prognosis, and LEP subgroup showed approximately 100 % 5-year survival. ACT was associated with a better DFS (HR, 0.70; 95 % CI 0.51-0.96, p = .026) for all stage IB patients. In SOL/MIP subgroup, patients could benefit from ACT for a significant improved DFS (HR, 0.81; 95 % CI 0.49-1.35; p = .030), but not for OS (HR, 0.39; 95 % CI 0.12-1.30, p = .111). In ACN/PAP subgroup, there was no significant benefit from ACT for both DFS (HR, 0.76; 95 % CI 0.54-1.08, p = .125) and OS (HR, 0.81; 95 % CI 0.49-1.35, p = .421). SOL/MIP predominant pattern was predictive for ACT benefit for DFS among invasive lung adenocarcinoma patients in stage IB.