Does the presence of a micropapillary component predict worse prognosis in pathological stage IA lung adenocarcinoma?

Considerable evidence has verified that the micropapillary pattern is significantly associated with worse prognosis in pulmonary adenocarcinoma. However, whether the presence of a micropapillary component in pathological stage IA lung adenocarcinoma is also related to worse prognosis remains unclear up to now. The aim of this meta-analysis was to identify the prognostic role of presence of a micropapillary component in pathological stage IA lung adenocarcinoma patients. Relevant studies were searched from the PubMed, EMBASE, Web of Science and CNKI databases and reviewed. The primary and secondary outcomes were the recurrence risk and long-term survival including the overall survival (OS) and disease-free survival (DFS), respectively. All statistical analysis were conducted by STATA 12.0 software. A total of 5257 lung adenocarcinoma patients at the pathological stage IA from ten retrospective studies were enrolled. The recurrence rates in pathological stage IA lung adenocarcinoma patients with and without the a micropapillary component were 32% [95% confidence interval (CI): 20%- 44%] and 7% (95% CI: 4%-10%) separately and pooled results indicated that presence of a micropapillary component was an obvious risk factor for recurrence [odds ratio (OR)= 3.41, 95% CI: 2.80-4.16, P＜0.001]. Besides, the presence of a micropapillary component was significantly related to poorer OS [hazard ratio (HR)= 2.44, 95% CI: 1.28-4.68, P = 0.007] and DFS (HR=2.60, 95% CI: 1.63-4.16, P＜0.001). Subgroup analysis focusing on invasive adenocarcinoma manifested consistent results. In pathological stage IA lung adenocarcinoma, the presence of a micropapillary component predicts obviously higher recurrence risk and worse prognosis even after focusing on invasive adenocarcinoma. However, more prospective high-quality studies are still needed to verify our findings.