Background: Thyroid transcription factor 1 (TTF-1) positivity correlates with a higher prevalence of epidermal growth factor receptor (EGFR) mutation in lung adenocarcinoma. It is unknown whether TTF-1 expression affects the clinical outcome of patients with advanced lung adenocarcinoma, who have received EGFR tyrosine kinase inhibitors (TKIs) during the treatment course.
Methods: This study enrolled patients with advanced lung adenocarcinoma who had results of EGFR mutation analysis and TTF-1 immunostaining. The impact of TTF-1 expression on overall survival (OS) and progression-free survival (PFS) under EGFR TKI treatment was evaluated. Multivariate analyses were done to examine the independent predictors of OS and PFS.
Results: Of 496 patients with advanced lung adenocarcinoma, 443 had TTF-1-positive adenocarcinoma. Patients with TTF-1-positive lung adenocarcinoma had longer OS than did those with TTF-1-negative lung adenocarcinoma (median survival, 27.4 vs 11.8 months, P = .001). In patients with EGFR TKI treatment, those with TTF-1-positive lung adenocarcinoma and mutant EGFR had longer OS. In patients with EGFR mutation, those with TTF-1-positive lung adenocarcinoma had longer PFS than did those with TTF-1-negative lung adenocarcinoma (median survival, 8.7 vs 5.7 months, P = .043). Multivariate analysis showed that negative TTF-1 expression is a predictor for shorter OS, and a predictor for shorter PFS under EGFR TKI treatment.
Conclusions: TTF-1 shows independent prognostic significance in advanced lung adenocarcinoma. Patients with TTF-1-negative lung adenocarcinoma have not only shorter OS, but also shorter PFS under EGFR TKI treatment, despite the existence of mutant EGFR. Further studies are needed to investigate the optimal treatment of patients with TTF-1-negative lung adenocarcinoma.