Identification of a low risk subgroup of stage IB lung adenocarcinoma patients

Several trials have recently reported the efficacy of adjuvant chemotherapy for resected stage IB non-small cell lung cancer (NSCLC). However, the histological findings and prognosis of stage IB lung adenocarcinoma vary considerably. The aim of this study was to investigate prognostic factors of resected stage IB adenocarcinoma and identify a subgroup with a better prognosis, in which adjuvant chemotherapy could be omitted.

We reviewed 413 cases of stage I lung adenocarcinoma treated by surgical resection, and investigated prognostic factors that favorably affected the survival of 106 patients with stage IB lung adenocarcinoma. A subgroup with a better outcome was identified and their survival was compared with that of stage IA patients.

The 5-year survival rate of the stage IB adenocarcinoma patients was 81.7%. Univariate analyses demonstrated that lymphatic permeation (p<0.001), vascular invasion (p=0.003), pleural invasion (p=0.001) and bronchioloalveolar carcinoma (BAC)-dominant histology (p=0.003) were significant prognostic factors. A multivariate analysis demonstrated that pleural invasion (p=0.02) was an independent prognostic factor. The 5-year survival rate of the stage IB adenocarcinoma patients without pleural invasion (76 cases) was 89.3%, and it was not statistically different from that of the stage IA patients (92.7%).

The stage IB lung adenocarcinoma patients without pleural invasion had a favorable outcome that was almost the same as that of stage IA patients. Because adverse effects of chemotherapy are sometimes severe and unacceptable, adjuvant chemotherapy can be omitted for stage IB adenocarcinoma without pleural invasion.