Prognostic significance and adjuvant chemotherapy survival benefits of a solid or micropapillary pattern in patients with resected stage IB lung adenocarcinoma.

OBJECTIVE: To evaluate the prognostic significance and beneficiaries of adjuvant chemotherapy (ACT) in various histological patterns of stage IB lung adenocarcinoma according to the 8th tumor-node-metastasis (TNM) classification. METHODS: A total of 1131 patients with pathological stage IB lung adenocarcinoma according to the 8th TNM classification who underwent lobectomy or segmentectomy were enrolled in this study. Based on the proportion of solid/micropapillary components, the patients were classified into 3 groups: solid/micropapillary-negative (SMPN) (n = 719; median survival, 49.7 months; interquartile range [IQR]. 35.1-67.0 months), solid/micropapillary-minor (SMPM; >5% but not predominant) (n = 272; median survival, 38.8 months; IQR, 26.6-51.5 months) and solid/micropapillary-predominant (SMPP; >5% and the most dominant) (n = 140; median survival, 39.6 months; IQR, 26.8-52.5 months). The predictors of disease-specific survival and recurrence-free survival were investigated. To reduce selection bias, propensity score-matching analysis was implemented before survival data were compared. RESULTS: Our data show significant differences in survival rates based on the proportion of solid/micropapillary patterns. The SMPM group had significantly higher cumulative incidences of lung cancer-specific death (P = .000) and recurrence (P = .000) compared with the SMPN group, so did the SMPP group when compared with SMPM patients (P = .000 for both). Multivariate analysis showed that the SMPM and SMPP patterns were poor prognostic factors for disease-specific survival (hazard ratio [HR], 1.86; 95% confidence interval [CI], 1.12-3.09 and HR, 4.56; 95% CI, 2.69-7.71, respectively) and recurrence-free survival (HR, 1.64; 95% CI, 1.20-2.24 and HR, 2.43; 95% CI, 1.64-3.60, respectively), as were older age, male sex, smoking history, larger tumor size, necrosis, and abnormal pulmonary function. Survival analysis stratified by histological pattern showed that patients with the SMPP pattern who received ACT had obviously lower cumulative incidences of lung cancer-specific death (HR, 0.46; 95% CI, 0.22-0.93; P = .031) and recurrence (HR, 0.48; 95% CI, 0.26-0.88; P = .017). CONCLUSIONS: Solid/micropapillary patterns were associated with poor prognosis, even if they were not predominant. ACT contributed to survival benefits in the SMPP subgroup of patients with stage IB lung adenocarcinoma.