Prognostic Role of Subtype Classification in Small-Sized Pathologic N0 Invasive Lung Adenocarcinoma.

Background The prognosis of patients with small, node-negative lung cancers, which the current indication for adjuvant chemotherapy never includes, is sometimes poor despite complete tumor resection. The present study aimed to identify independent prognostic factors and to clarify possible candidates for adjuvant chemotherapy among patients with small, node-negative invasive adenocarcinoma. Methods This study involved 153 patients with completely resected small (≤20 mm) pathologic N0 invasive adenocarcinomas. Invasive adenocarcinoma was classified as lepidic predominant (LPA), papillary or acinar predominant (PA), or solid or micropapillary predominant (SM), according to the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society classification. Overall survival and recurrence-free survival were estimated from Kaplan-Meier curves. Prognostic factors for recurrence-free survival were determined using univariate and multivariate Cox proportional hazards models. Results Three-year overall survival and recurrence-free survival rates were 98% and 98%, 97% and 88%, and 85% and 64% for LPA, PA, and SM tumors, respectively. Prognosis was the worst for patients with SM tumors (overall survival LPA versus PA, p = 0.099; LPA versus SM, p 0.001; and PA versus SM, p = 0.032; recurrence-free survival LPA versus PA, p = 0.014; LPA versus SM, p 0.001; and PA versus SM, p 0.001). Subtype was a significantly independent prognostic factor for recurrence-free survival in multivariate analysis (SM versus LPA hazard ratio 22, 95% confidence interval: 2.5 to 190, p  = 0.0054). Conclusions Patients with small (≤20 mm) pathologic N0 solid or micropapillary predominant invasive adenocarcinoma might be possible candidates for adjuvant chemotherapy.