Prognostic impact according to the proportion of the lepidic subtype in stage IA acinar-predominant lung adenocarcinoma.

BACKGROUND Adenocarcinoma is the most common type of lung cancer and most adenocarcinomas have heterogeneous subtypes. Acinar-predominant adenocarcinoma is the most common. This study aimed to identify the prognostic impact of other mixed histological subtypes in acinar-predominant lung adenocarcinoma. METHODS The medical records of patients with pathological stage IA acinar-predominant lung adenocarcinoma between January 2010 and April 2016 were reviewed. The patients were divided into two groups according to the proportion of the lepidic subtype, with a cutoff value of 20%, and prognostic factors were analyzed. RESULTS A total of 215 patients with stage IA acinar-predominant adenocarcinoma were reviewed. The 20% or more lepidic subtype group had a low value of SUVmax (p = 0.001), good differentiation (p < 0.001) and a low incidence of the solid histological subtype (p = 0.016). Recurrence was significantly lower in the 20% or more lepidic subtype group (p = 0.008). The disease-free survival (p = 0.007) and overall survival (p = 0.046) were significantly different between the two groups. Multivariate analysis showed that lymphovascular invasion (p = 0.006) and no or less than 20% lepidic subtype (p = 0.036) were significant prognostic factors for disease-free survival. CONCLUSIONS The lepidic proportion may be useful to predict recurrence in acinar-predominant stage IA lung adenocarcinoma.