Micropapillary or solid pattern predicts recurrence free survival benefit from adjuvant chemotherapy in patients with stage IB lung adenocarcinoma

Background: Our study aimed to evaluate the prognostic significance and adjuvant chemotherapy (ACT) benefits of a micropapillary/solid (MS) pattern in patients with stage IB lung adenocarcinoma. Methods: Patients with pathologically-confirmed stage IB adenocarcinoma who underwent surgical resection between January 2009 and December 2011 were included. The tumors were reclassified into three categories: MS patterns absent (MS-); non-predominant MS patterns (MS+); predominant MS (MS++). The correlations of prognosis and ACT with recurrence-free survival (RFS) were evaluated. Results: Overall, 497 (MS-, n=269; MS+, n=177; MS++, n=51) patients were enrolled in the study. In univariate analysis, the MS+ [hazard ratio (HR), 1.437; 95% confidence interval (CI), 1.030-2.006; P=0.033] and MS++ (HR, 2.818; 95% CI, 1.792-4.432; P<0.001) groups had significantly poor prognosis compared with MS-group. Multivariate analysis revealed that age >= 65 (HR, 1.504; 95% CI, 1.077-2.099; P=0.017), serum level of carcinoembryonic antigen (CEA) >= 10 ng/mL (HR, 1.658; 95% CI, 1.048-2.623; P=0.031) and MS++ (HR, 2.529; 95% CI, 1.550-4.126; P<0.001) were significant prognostic factors. Furthermore, subgroup analysis showed that MS++ patients but not MS-and MS+ derived RFS (recurrence-free survival) benefit from ACT (HR, 0.357; 95% CI, 0.152-0.836; P=0.018). Conclusions: MS pattern successfully differentiated the prognosis difference among stage IB lung adenocarcinomas and identified patients who benefitted from ACT.