The adjuvant chemotherapy can be omitted for lepidic predominant lung adenocarcinoma in stage IB of the 8th TNM staging system.

Abstract ObjectivesThis study was designed to investigate whether the outcomes of adjuvant chemotherapy are affected by the lung adenocarcinoma predominant (AP) in stage IB according to the 8th UICC staging system. Methods From 2008 through 2015, 293 patients with pathological stage IB who were ≤ 75-year-old and underwent lobectomy were studied. The relations of clinicopathological factors were investigated by propensity score matching.ResultsThe median follow-up period was 66.0 months. The cases of AP were followed: lepidic 96, acinar 71, papillary 54, solid 45, micropapillary 3 and others 17. Adjuvant chemotherapy with UFT was performed in 70 cases (23.9%). Recurrence-free survival at 5 years (RFS) was 72.2%. Lymph vessel invasion (ly+), vascular vessel invasion (v+), pleural invasion (pl+) and non-lepidic statistically affected RFS. Multivariate analysis showed that only AP (non-lepidic) was significant (hazard ratio; HR=2.006 (1.104-3.644)). Overall survival (OS) rate at 5 years was 83.5%. ly+, v+, pl+, EGFR mutation status and AP affected OS. In multivariate analysis, only non-lepidic was left (HR=2.888 (1.231 - 6.774)). After matching AP, adjuvant chemotherapy did not have an impact on RFS or OS (p=0.992, 0.616). In lepidic, both adjuvant and non-adjuvant had excellent outcomes in RFS (84.8% and 92.9%, p=0.574) and OS (100% vs 100%, p=0.361). In non-lepidic group, adjuvant therapy tended to show slightly, but not significantly better RFS (71.5% vs, 60.6%, p=0.177). ConclusionLepidic predominant showed excellent outcomes, adjuvant chemotherapy is not necessary. For non-lepidic predominant, UFT remains standard adjuvant chemotherapy in Japan.