Impact of proposed IASLC/ATS/ERS classification of lung adenocarcinoma: prognostic subgroups and implications for further revision of staging based on analysis of 514 stage I cases

A new lung adenocarcinoma classification is being proposed by the International Association for the Study of Lung Cancer, American Thoracic Society and European Respiratory Society (IASLC/ATS/ERS). This proposal has not yet been tested in clinical datasets to determine whether it defines prognostically significant subgroups of lung adenocarcinoma. In all, 514 patients who had pathological stage I adenocarcinoma of the lung classified according to the Union for International Cancer Control/American Joint Committee on Cancer 7th Edition, and who had undergone a lobectomy with mediastinal lymph node dissection were retrospectively reviewed. Comprehensive histological subtyping was used to estimate the percentage of each histological subtype and to identify the predominant subtype. Tumors were classified according to the proposed new IASLC/ATS/ERS adenocarcinoma classification. Statistical analyses were made including Kaplan–Meier and Cox regression analyses. There were 323 females (63%) and 191 males (37%) with a median age of 69 years (33–89 years) and 298 stage IA and 216 stage IB patients. Three overall prognostic groups were identified: low grade: adenocarcinoma in situ ( n =1) and minimally invasive adenocarcinoma ( n =8) had 100% 5-year disease-free survival; intermediate grade: non-mucinous lepidic predominant ( n =29), papillary predominant ( n =143) and acinar predominant ( n =232) with 90, 83 and 84% 5-year disease-free survival, respectively; and high grade: invasive mucinous adenocarcinoma ( n =13), colloid predominant ( n =9), solid predominant ( n =67) and micropapillary predominant ( n =12), with 75, 7170 and 67%, 5-year disease-free survival, respectively ( P