The New Histologic Classification of Lung Primary Adenocarcinoma Subtypes Is a Reliable Prognostic Marker and Identifies Tumors With Different Mutation Status

BACKGROUND: Histologic classification of lung adenocarcinoma subtype has a prognostic value in most studies. However, lung adenocarcinoma characteristics differ across countries. Here, we aimed at validating the prognostic value of this classification in a large French series of lung adenocarcinoma. METHODS: We reviewed 407 consecutive lung adenocarcinomas operated on between 2001 and 2005 and reclassified them according to the International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) classification and subsequently graded them into low, intermediate, and high grade. We analyzed the relevance of this classification according to clinical, pathologic, and molecular analysis. RESULTS: Patients (median age, 61 years; 288 men) underwent lobectomy (n = 378) or pneumonectomy (n = 29). Patients' overall survival at 5 and 10 years was 53.2% and 32.6%, respectively. Union for International Cancer Control stage distribution was 189 stage I, 104 stage II, 107 stage III, and seven stage IV. Low-grade tumor was found in one patient, intermediate grade in 275 patients, and high grade in 131 patients. KRAS and EGFR mutations were detected in 34% and 9.6%, respectively. Histologic grade was significantly correlated with extent of resection (P =.01), thyroid transcriptional factor-1 expression (P = .00000001), vascular emboli (P = .03), and EGFR mutations (P = .01). Mucinous adenocarcinomas were associated with KRAS mutations (P = .003). At univariate analysis, age, extent of resection, histologic grade, pleural invasion, vascular emboli, pathologic T and N, and stage were predictive of survival. At multivariate analysis, age (P = .0001), histologic grade (P = .03), and stage (P = .000003) were independent prognostic factors. CONCLUSIONS: IASLC/ATS/ERS classification of lung adenocarcinomas predicts survival in French population. Histologic grade correlates with clinical, pathologic and molecular parameters suggesting different oncogenic pathways.