Long-Term Prognosis and Prognostic Indicators of Stage IA Lung Adenocarcinoma

Background The 8th edition of the TNM stage classification of lung cancer was developed based on an evaluation of the 5-year prognosis using an international database. Since recurrence after 5 years postoperatively is known to develop, the applicability of the stage classification beyond 5 years after treatment needs to be evaluated. Patients and Methods Postoperative prognosis and prognostic indicators were analyzed using data for 648 patients of pathological stage IA adenocarcinoma, who underwent complete resection between 2007 and 2012. Results The median age was 66 years (interquartile range 60–73 years), and the median follow-up duration was 100 months (interquartile range 70–116 months). Overall survival probabilities for pathological stage IA1, IA2, and IA3 patients were 100%, 96.3%, and 91.5% at 5 postoperative years, and 94.2%, 89.8%, and 83.5% at 10 postoperative years, respectively (IA1 vs IA2: p = 0.05; IA2 vs IA3: p = 0.05). Multivariate analysis for overall survival of patients who survived without recurrence for 5 postoperative years revealed that age (hazard ratio 3.21, p = 0.02) was the only factor that was significantly associated with long-term survival. Stage classification (IA1, IA2, or IA3) was not an associated factor. The incidence of secondary primary lung cancer continued to increase, resulting in an estimated probability of 8.6% at 10 postoperative years. Conclusions For patients who survived without recurrence for 5 postoperative years, age, not stage classification, was associated with survival thereafter. The long-term follow-up strategy does not need to be modified according to the stage classification, and screening for secondary primary lung cancer should be considered.