Impact of Solid Minor Histologic Subtype in Postsurgical Prognosis of Stage I Lung Adenocarcinoma

Background. Few studies focus on the outcome and effect of a postsurgical treatment strategy for early stage patients with minor solid components pattern. This study investigated the prognosis and the adjuvant chemotherapy benefit among stage I invasive lung adenocarcinoma patients with minor solid components pattern according to the eighth TNM staging classification. Methods. A total of 3,308 lung adenocarcinoma patients with mixed histologic components was divided into three groups: solid predominant, solid minor, and solid absent pattern. Disease-free survival and overall survival were analyzed to evaluate survival difference among patients in the different groups using the KaplanMeier approach and multivariable Cox models. Results. Both solid predominant and solid minor groups showed significantly worse disease-free survival (p < 0.001) and overall survival (p < 0.001) compared with the solid absent group. There were no significant diseasefree survival (hazard ratio [HR] 1.41, 95% confidence interval [CI]: 0.87 to 2.30, p = 0.161) or overall survival (HR 1.60, 95% CI: 0.83 to 3.09, p = 0.159) difference between the former two groups. For patients in stage IB, adjuvant chemotherapy improves disease-free survival (HR 0.33, 95% CI: 0.11 to 1.02, p = 0.044) but not overall survival (HR 0.61, 95% CI: 0.21 to 1.77, p = 0.360) in the solid predominant group. No adjuvant chemotherapy benefits for disease-free survival (HR 1.04, 95% CI: 0.49 to 2.22; p = 0.922) and overall survival (HR 0.49, 95% CI: 0.13 to 1.90; p = 0.291) were seen for the solid minor group. Conclusions. Solid minor components predict a significantly worse prognosis compared with the solid absent pattern. However, adjuvant chemotherapy may be unhelpful to improve outcomes for stage IB patients with solid minor components after surgery. (C) 2018 by The Society of Thoracic Surgeons