Oncological characteristics of EGFR-mutated clinical stage IA lung adenocarcinoma with radiologically pure-solid appearance

We evaluated the clinicopathological and oncological characteristics of epidermal growth factor receptor (EGFR)-mutated clinical stage IA radiological pure-solid lung adenocarcinoma and compared them with those of a ground-glass opacity (GGO) component.Between 2008 and 2020, data from 1014 surgically resected clinical stage 0-IA EGFR-mutated lung adenocarcinomas were evaluated. Oncological outcomes were assessed using multivariable analysis. Overall survival (OS) was estimated using Kaplan-Meier analysis and the log-rank test. The cumulative incidence of recurrence (CIR) was estimated using the Gray's test.Of these, 233 (23%) were radiologically pure-solid tumors, which demonstrated a higher proportion of nodal metastasis, micropapillary component, spread through alveolar space, and Ex19 subtype compared to those of tumors with GGO (p<0.001). Multivariable analysis revealed that the presence of GGO was an independently significant factor for OS (p=0.037) and CIR (p<0.001). In cases where the oncological outcomes were stratified by the presence of GGO component, the 5-year OS was excellent at more than 90% in tumors with GGO despite clinical-T categories (p=0.2044); however, tumor size significantly affected survival only in pure-solid tumors (T1a,100%; T1b,77.7%; T1c,68.5%; p=0.0056). Furthermore, the CIR was low in tumors with GGO despite the clinical-T categories, whereas tumor size significantly affected the CIR only in pure-solid tumors (5-year CIR: T1a-b,18.9%; T1c,41.3%; p<0.001).Oncologic behavior and prognosis of radiologically pure-solid tumors were significantly poorer than those of tumors with GGO among patients with EGFR-mutated early-stage lung adenocarcinoma. These findings imply distinct tumorigenesis based on the presence of GGOs, even in tumors with EGFR mutations. (250 words).