Thyroid transcription factor 1 (TTF‐1) negativity as a predictor of unfavorable response to EGFR‐TKI therapy in advanced lung adenocarcinoma patients with EGFR mutations

BACKGROUND: The absence of thyroid transcription factor 1 (TTF‐1) is associated with a lower frequency of epidermal growth factor receptor (EGFR) mutations in lung adenocarcinoma (LUAD). The aim of this study was to assess the impact of TTF‐1 expression on the clinical response to EGFR‐tyrosine kinase inhibitor (TKI) treatment in patients with advanced LUAD. METHODS: The data of patients with advanced LUAD who were admitted to the Beijing Tiantan Hospital and Peking University Cancer Hospital (China) between April 2009 and May 2023 was retrospectively analyzed. RESULTS: A total of 227 patients diagnosed with advanced LUAD were included, of which 28.2% (64/227) had TTF‐1‐negative adenocarcinoma, while 54.6% (124/227) harbored EGFR mutations. Negative TTF‐1 expression significantly correlated with male sex (68.8% vs. 42.3%, p < 0.001), history of heavy smoking (57.8% vs. 36.2%, p = 0.003), poorly differentiated tumors (86.5% vs. 43.2%, p < 0.001), and lower frequency of EGFR mutations (26.6% vs. 65.6%, p < 0.001) compared with TTF‐1 positivity. Multivariable logistic regression showed that low prevalence of EGFR mutations (p < 0.001) and male sex (p = 0.006) were independent predictive factors for the negative expression of TTF‐1. Patients lacking TTF‐1 also exhibited worse overall response rate (ORR; 23.5% vs. 54.2%, p = 0.019), disease control rate (DCR; 58.8% vs. 89.7%, p = 0.003), and median progression‐free survival (PFS; 2.9 vs. 11.6 months, p < 0.001) following treatment with EGFR‐TKIs compared to the TTF‐1‐positive patients with EGFR mutations. CONCLUSIONS: Patients with TTF‐1‐negative and EGFR‐mutant LUAD show a diminished response to EGFR‐TKIs.