Evaluation of the novel International Association for the Study of Lung Cancer grading system in adenocarcinoma with spread through air space.

BACKGROUND

The International Association for the Study of Lung Cancer (IASLC) pathology panel has proposed a new grading system for invasive lung adenocarcinoma (LADC). This study aims to validate this novel grading system for invasive LADC using propensity score matching (PSM), with a specific focus on patients exhibiting spread through air space (STAS).

METHODS

We retrospectively analyzed the clinicopathologic features of a large cohort of 910 non-mucinous LADCs with STAS from 2017 to 2020 and classified them according to the novel grading system. We applied PSM to adjust for potential confounders between the grading groups. Kaplan-Meier and Cox proportional hazards models were adopted for prognostic evaluation.

RESULTS

The results showed that the IASLC grading system (grades 2 and 3) stratified well in terms of recurrence-free survival (RFS) and overall survival (OS) (P0.02 and P0.02, respectively) after matching, with Grade 3 being an independent predictor of RFS [hazard ratio (HR), 1.533; P0.02] and OS (HR, 2.765; P0.02) in multivariable models. The concordance index (C-index) and area under the curve (AUC) of the IASLC system were 0.719 and 0.754 for recurrence and 0.844 and 0.891 for death, respectively. In addition, anaplastic lymphoma kinase () fusion and tumor protein p53 () mutations were detected more frequently in grade 3 tumors, while epidermal growth factor receptor () mutations were more prevalent in grade 2 tumors. The IASLC grade did not predict the benefit of adjuvant chemotherapy (ACT).

CONCLUSIONS

This study suggests that the new IASLC grading system is a valuable prognostic tool for patients with STAS-positive LADC.