Association between EGFR-TKI resistance and efficacy of radiotherapy for brain metastases from EGFR-mutant lung adenocarcinoma

Aim: To clarify how patients with epidermal growth factor receptor (EGFR)-mutant lung adenocarcinoma with acquired resistance to EGFR-tyrosine kinase inhibitors (TKIs) respond to radiotherapy (RT) for brain metastases. Patients and Methods: Forty-seven patients were divided into the following three groups: a TKI-naïve group with EGFR mutation (n=11), a TKI-resistant group with EGFR mutation (n=10), and an EGFR-wild-type group (n=26). Patients received stereotactic RT (n=23) or whole-brain RT (n=24). Results: The response rate for patients with TKI-resistant tumor at three months after RT tended to be lower (11%) than that of those who were TKI-naïve (82%, p=0.006) and for patients with wild-type EGFR (48%, p=0.10). On univariate analysis, central nervous system progression-free and overall survival were significantly shorter for patients with TKI-resistant tumors than for those who were TKI-naïve (p=0.018 and p=0.005, respectively). Multivariate analysis showed that TKI resistance was an independent predictor of poorer overall survival (p=0.011). Conclusion: Acquired resistance to TKIs appears to be associated with low efficacy of brain RT.