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The current grading system only includes six pathological subtypes. In clinical work, we would encounter mucinous adenocarcinoma and mixed adenocarcinoma containing both mucinous and non-mucinous adenocarcinoma. And none of these types can be applied with grading systems to classify risk levels and predict prognosis. This retrospective study included 553 patients with lung invasive adenocarcinoma with or without LIMA components (stage I–III) from Shanghai Chest Hospital and 6962 patients in the SEER database. We introduced the LIMA and re-classified the IASLC grading system. The validity of the revised grading, derived from the training cohort, was measured in the validation cohort (the SEER database), using the concordance index (Harrell C-index), time-dependent receiver operating characteristic (ROC) curves and area under the curves (AUCs). Overall survival (OS) curves were estimated by a Kaplan–Meier method and log-rank test was performed to compare differences. The LIMA was classified as predominant tumor patterns in the IASLC grading system, and mucinous predominant tumors with no or less than 20% of high-grade patterns (solid, micro papillary, and/or complex glandular patterns) were classified as the Grade 2 (moderately differentiated). The C-index and AUCs of the revised IASLC system were 0.754 and 0.729 in the training cohort and 0.716 and 0.682 in the validation cohort, respectively. Moreover, the revised grading showed a 5-year OS rate of 88.6% in Grade I group, 76.1% in Grade II group, 65.5% in Grade III group in the training cohort (P<0.001). The revised grading also showed a promising performance in distinguishing patients in the validation cohort (5-year OS rate: 85.4% vs. 69.8% vs. 60.1%, P<0.001). The revised IASLC grading system was practical and prognostic for lung invasive adenocarcinoma with or without LIMA component, and the introduction of LIMA could improve its applicability.
Li et al. (Fri,) studied this question.