Validation of the Eighth Edition Clinical T Categorization System for Clinical Stage IA, Resected Lung Adenocarcinomas: Prognostic Implications of the Ground-Glass Opacity Component.

INTRODUCTION: There is controversy regarding the clinical T (cT) category of lung adenocarcinomas that manifest as part-solid nodules (PSNs). We aimed to validate the cT category and to evaluate the independent prognostic role of the nodule type (i.e., part-solid versus solid). METHODS: We retrospectively evaluated the prognostic value of clinico-radiologic factors regarding the overall survival of patients with clinical stage IA lung adenocarcinomas that were resected between 2008 and 2014. cT Category, nodule type, and their interaction term were included in the multivariable Cox regression analysis with other variables. In addition, a mixture cure model analysis was performed to investigate the association between the covariates and long-term survival. RESULTS: A total of 744 patients (420 women; 362 PSNs; median age, 63 y) were included. The multivariable-adjusted hazard ratio (HR) of the nodule type was not significant (1.30, 95% confidence interval [CI]: 0.80-2.10, p = 0.291). However, the cT categories were significantly associated with overall survival (HR of cT1b, 2.33 [95% CI: 1.07-5.06, p = 0.033]; HR of cT1c, 5.74 [95% CI: 2.51-13.12, p < 0.001]). There were no interactions between the nodule type and the cT categories (all p > 0.05). The multivariable mixture cure model revealed that solid nodules were associated with a decreased probability of long-term survival (OR = 0.40, 95% CI: 0.18-0.92, p = 0.030). In addition, cT1c was a negative predictor of long-term survival (OR = 0.26, 95% CI: 0.07-0.94, p = 0.040). CONCLUSIONS: The cT categorization system is valid for PSNs and solid nodules. Nevertheless, PSNs are a prognostic factor associated with long-term survival.