Outcomes of patients with different lepidic percentage and tumor size of stage I lung adenocarcinoma

BACKGROUND: To evaluate the long‐term outcomes after surgical resection for stage I lung adenocarcinoma based on the percentage of lepidic component (LC) and invasive tumor size (IS). METHODS: The clinicopathological characteristics of 1049 patients with stage I lung adenocarcinoma who underwent surgery between 2006 and 2016 were retrospectively reviewed. Tumors were categorized into groups: A (LC ≥ 50%) and B (LC < 50%). Groups A0 and A1 consisted of minimally invasive adenocarcinomas (MIA) and other lepidic‐predominant invasive adenocarcinomas, respectively. Group B was categorized into B1 (IS ≤ 1 cm), B2 (1 < IS≤2 cm), and B3 (2 < IS≤3 cm) by invasive tumor size and divided into subgroups (B1[lep+]/[lep−], B2[lep+]/[lep−], and B3[lep+]/[lep−]) according to the presence[lep+] or absence[lep−] of LCs. Cumulative incidence of recurrence (CIR) and cancer‐specific survival (CSS) were examined. RESULTS: LC decreased with increasing IS. Only 24 (8.5%) tumors in group A had an IS >1 cm. 10‐year CIR and CSS were 15.2% and 86.0%. LC and IS were found to be independent predictors of CSS. Patients in group A had 1.4% 10‐year CIR and 100% 10‐year CSS. In group B, a significantly higher CIR and worse CSS were observed as IS increased (p < 0.001), but LC was not a predictor for CSS (p = 0.593). No significant differences in CIR or CSS were found in presence of LC or not when LC < 50% (B1[lep+]/[lep−], B2[lep+]/[lep−], and B3[lep+]/[lep−]: p = 0.36/0.48, p = 0.82/0.94, and p = 0.90/0.37, respectively). CONCLUSIONS: LC≥50% tumors demonstrated excellent prognosis regardless of IS. The outcomes of LC < 50% tumors were well predicted by IS, corresponding to the T‐staging system. The predictive value of LC for prognosis became insignificant.