Background: This study aimed at identifying risk factors of recurrence for completely resected pathologic T1aN0M0 lung adenocarcinomas.
Methods: We reviewed the records of 177 T1aN0M0 invasive adenocarcinoma patients, and re-classified achieved surgical specimens according to the new International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society (IASLC/ATS/ERS) lung adenocarcinoma classification. Impact on recurrence-free survival (RFS) for age, gender, smoking history, lymphovascular invasion (LVI) and new classification was analyzed by log-rank test and Cox regression. Two existing prognostic grouping schemes of new classification were compared, and subsequently, the correlation of high-grade group in the better prognostic grouping model with clinical data was investigated statistically.
Results: The 5-year recurrence-free rate was 83.7%. The LVI and new adenocarcinoma classification were significantly associated with 5-year RFS (P = 0.012; P = 0.022, respectively). The designation of papillary predominant subtype in the low-grade group, along with lepidic- and acinar predominant subtype had more prognostic significance than the model of combining papillary-, solid- and micropapillary predominant subtypes as the high-grade group (P = 0.005 versus P = 0.181). This high-grade group has increased risk of recurrence in a multivariate Cox regression (adjusted HR 2.815, 95% CI: 1.239 to 6.397, P = 0.013), and is associated significantly more with male gender (adjusted OR 2.214, 95% CI: 1.050 to 4.668, P = 0.037), and, with borderline significance, the presence of LVI (adjusted OR 2.091, 95% CI: 0.938 to 4.662, P = 0.071).
Conclusions: Our results showed that the solid- and micropapillary predominant subtype of IASLC/ATS/ERS classification remains the only risk factor for post-operative recurrence of T1aN0M0 adenocarcinomas, suggesting that they can be indicators of aggressive tumor behaviors.