Association of IASLC/ATS/ERS Histologic Subtypes of Lung Adenocarcinoma With Epidermal Growth Factor Receptor Mutations in 320 Resected Cases

Abstract

BackgroundThe relationships between the subtypes defined by the new international histologic classification of lung adenocarcinoma (IASLC/ATS/ERS) and epidermal growth factor receptor (EGFR) mutations were studied. Patients and MethodsWe retrospectively reviewed 320 patients with lung adenocarcinoma (162 women, 158 men; mean age, 69 years) who had undergone complete resection, focusing on the new histologic subtypes and EGFR mutations. The clinical stage was IA in 196 patients, IB in 95, IIA in 10, IIB in 10, IIIA in 6, and IV in 3. ResultsThe most prevalent subtype was papillary (35.0%), followed by acinar (29.4%), lepidic (13.1%), solid (7.2%), adenocarcinoma in situ (6.6%), minimally invasive adenocarcinoma (6.3%), micropapillary (1.6%), and invasive mucinous adenocarcinoma (1.0%). These subtypes were predictive for both postoperative disease-free and overall survival. EGFR mutations, detected in 40.6% of all cases, were most frequent in acinar (48.4%), followed by minimally invasive adenocarcinoma (45.0%) and papillary (43.8%). They were least frequent in the solid subtype (17.4%). EGFR mutation status did not affect postoperative disease-free or overall survival. ConclusionThe outcome after complete resection for lung adenocarcinoma was predicted by the proposed subtype classification. Because EGFR mutations were found in all subtypes, mutation analyses are essential to identify patients with postoperative relapse who would benefit from EGFR-tyrosine kinase inhibitor therapy.