Conventional chest CT features are associated with Ki-67 labeling index in lung adenocarcinoma: a single-center retrospective radiopathologic study.

BACKGROUND: Ki-67 labeling index (LI) reflects tumor proliferative activity but requires pathological specimens and may be affected by sampling heterogeneity. This study evaluated associations between conventional chest computed tomography (CT) features and Ki-67 LI in lung adenocarcinoma. METHODS: This single-center retrospective study included patients with pathologically confirmed primary lung adenocarcinoma who underwent pretreatment chest CT and Ki-67 immunohistochemistry between January 2021 and January 2025. Ki-67 LI ≥20% was used as the primary threshold for analysis. Clinicopathological characteristics and CT features were compared between the Ki-67 LI <20% and Ki-67 LI ≥20% groups. Univariable and multivariable logistic regression analyses were performed, adjusting for age, sex, smoking status, clinical stage, tumor differentiation, and specimen type. Sensitivity analyses used a 30% Ki-67 threshold and a surgical-specimen subgroup. RESULTS: Among 252 included patients, 125 had low Ki-67 LI and 127 had Ki-67 LI ≥20%. Ki-67 LI ≥20% was associated with aggressive clinicopathological features, including unfavorable growth pattern, poor differentiation, advanced stage, N-positive disease, visceral pleural invasion, and lymphovascular invasion. On CT, Ki-67 LI ≥20% tumors had larger maximum diameter, higher consolidation-to-tumor ratio, more frequent solid appearance, and more pleural indentation. In multivariable analysis, pleural indentation was the only CT feature that retained a significant adjusted association with Ki-67 LI ≥20% (adjusted odds ratio, 2.07; 95% confidence interval, 1.15-3.73; P=0.02). This association persisted in the surgical-specimen subgroup but was not reproduced when Ki-67 LI ≥30% was used as the alternative threshold. CONCLUSIONS: In lung adenocarcinoma, pleural indentation was the most stable conventional CT feature independently associated with Ki-67 LI ≥20%. Conventional CT may provide accessible clues to tumor proliferation but should complement pathological Ki-67 assessment.