The importance of the lepidic component as a prognostic factor in stage I pulmonary adenocarcinoma

Background: Stage I pulmonary adenocarcinoma (PA) can offer an unfavorable prognosis. The aim of this study was to classify the prognosis of stage I PA on the basis of the lepidic component and to confirm whether the lepidic component can be used as a criterion for predicting the prognosis of stage I PA. Methods: We conducted a retrospective study of patients who underwent curative surgery for stage I and IIA PA. Stage I disease was divided into three groups on the basis of the lepidic component: group 1, ≤10%; group 2, >10 to 50%; and group 3, >50%. We compared recurrence-free survival (RFS) rates among groups 1, 2, and 3, and stage IIA disease. We also evaluated risk factors for disease recurrence with multivariate analysis. Results: A total of 224 patients were included in our study; most patients (n=201) had stage I disease. Three-year RFS rates in group 1 (n=73), group 2 (n=75), and group 3 (n=53) were 74.1, 90.4, and 90.0%, respectively. There was a significant difference in RFS between group 1 and group 2 (p=0.009). The 3-year RFS rate in stage IIA disease was 61.4%. There were no significant differences in RFS between group 1 and stage IIA disease (p=0.163). In multivariate analysis, group 1 had the highest risk of recurrence (HR 5.806, p=0.006) in stage I PA. Conclusions: Stage I PA with a lepidic component ≤10% was associated with an unfavorable prognosis that was similar to the prognosis of stage IIA disease. The prognosis for stage I PA should not be based on general criteria, but instead, the lepidic component should be evaluated and considered when determining disease prognosis.