A histological grading system for invasive lung adenocarcinoma has been proposed by the International Association for the Study of Lung Cancer (IASLC) Pathology Committee in June 2020. This study evaluated the prognostic value of the IASLC histologic grading system (the IASLC system) in a large Japanese cohort.
We performed comprehensive histological subtyping using the semiquantitative estimation of five major patterns and complex glandular patterns (CGPs) in patients with a completely resected lung adenocarcinoma and determined the histological grade using the IASLC system. Concordance index (C-index) and receiver operating characteristic curves were used to evaluate the clinical utility of the IASLC system for recurrence and death; the comparison was performed with the architectural-pattern system (the Arch system) and the grading system based on the two most predominant patterns (the Sica’s system).
Of 1,002 patients with invasive ADC, 235 had recurrent disease and 166 died of lung cancer. The C-index and area under the curve of the IASLC system were 0.777 and 0.807, respectively, for recurrence and 0.767 and 0.776, respectively, for death. These were similar to those of the Arch system (0.763 and 0.796 for recurrence, 0.743 and 0.755 for death) and the Sica’s system (0.786 and 0.814 for recurrence, 0.762 and 0.773 for death).
We demonstrated that the IASLC system for invasive lung adenocarcinoma has prognostic significance by examining a large Japanese cohort. We believe that the IASLC grading system will provide physicians with better information for post-surgery treatment.

Copyright © 2021. Published by Elsevier Inc.