Objective To investigate the value of lung adenocarcinoma classification developed by International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society ( IASLC/ATS/ERS) in predicting the effect of three-dimensional radiotherapy ( 3DRT) after surgery for locally advanced lung adenocarcinoma.Methods The clinical data of 150 patients with invasive lung adenocarcinoma who underwent radical resection and systematic lymph node dissection in Tianjin Medical University from 2010 to 2013 were analyzed, and according to the IASLC/ATS/ERS classification, they were divided into lepidic predominant group (LEP group), acinar predominant group (ACN group), papillary predominant group (PAP group), micropapillary predominant group (MIP group), and solid predominant group (SOL group), and further divided into LEP group, CAN/PAP group, and MIP/SOL group.The overall survival ( OS) and disease-free survival ( DFS) rates were compared between groups.The Kaplan-Meier method was used to calculate survival rates, the log-rank test was used for survival difference analysis and univariate prognostic analysis, and the Cox proportional hazards model was used for multivariate prognostic analysis.Results Among all the patients, the median OS and DFS rates were 30.8 and 25.8 months, respectively.For the patients in the LEP group, ACN/PAP group, and MIP/SOL group, the median OS rates were 40.0, 32.2, and 28.4 months, respectively ( P=0.005) , and the median DFS rates were 29.2, 25.8, and 24.2 months, respectively ( P=0.011) .For the ACN/PAP group, the patients who received or did not receive radiotherapy had a median OS rate of 37.4 or 25.3 months ( P=0.000) and a DFS rate of 31.1 or 25.2 months (P=0.000).For the MIP/SOL group, the patients who received or did
not receive radiotherapy had a median OS rate of 28.3 or 27.4 months ( P=0.783) and a DFS rate of 25.3 or 24.0 months ( P=0.732 ) .Conclusions The IASLC/ATS/ERS classification helps to predict the prognosis of patients with locally advanced invasive lung adenocarcinoma who receive postoperative radiotherapy.Postoperative radiotherapy can be performed for ACN and PAP patients, while there is no need to perform radiotherapy for MIP and SOL patients .