Non-BAC Component but not Epidermal Growth Factor Receptor Gene Mutation is Associated with Poor Outcomes in Small Adenocarcinoma of the Lung

Objective: The purpose of this study was to identify risk factors for poor clinical outcome after surgical resection of small lung adenocarcinoma. Materials and Methods: Clinical records of 127 patients who had pathologic stage IA lung adenocarcinoma 20 mm or less and who had undergone a lobectomy with mediastinal lymph node dissection were reviewed. The percentage of non-bronchioloalveolar carcinoma (non-BAC) components quantified objectively, and epidermal growth factor receptor gene (EGFR) mutation determined by polymerase chain reaction-based assay were retrospectively linked with clinical data. Results: Based on the percentage of non-BAC component, 127 patients were classified as follows: 26 in group I, BAC, 46 in group II mixed subtype with ≥ 50% BAC, 18 in group III, mixed subtype with under 50% BAC, and 37 in group IV, mixed subtype with all non-BAC components or a pure pattern of one of the non-BAC components. Groups I and II were considered to be a “low non-BAC component type” and groups III and IV were considered to be a “high non-BAC component type.” EGFR mutations in exon19 and exon21 were observed in 64 patients (50.4%). In terms of recurrence, the high non-BAC component type was the only independent factor for recurrence (p = 0.029). Regarding survival, the high age (p = 0.028) and high non-BAC component type (p = 0.046) were independent risk factors for poor overall survival. They were also independent risk factors for poor disease-free survival (p = 0.025 and p = 0.027, respectively). Conclusion: The high non-BAC component but not EGFR mutation status, is an independent risk factor for both recurrence and poor prognosis in patients with stage IA lung adenocarcinoma ≤20 mm.