Analysis of metastases in non-small cell lung cancer patients with epidermal growth factor receptor mutation

BACKGROUND: Most lung cancer patients are diagnosed at an advanced stage with metastases. There was no population-based data on metastases in non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor (EGFR) mutation. This study focused on the metastases in NSCLC patients with EGFR mutation. METHODS: In our research, we retrospectively studied 365 NSCLC patients with EGFR mutation (EGFR positive-mutant group) were not resistant to first-generation EGFR TKIs and 316 NSCLC patients with T790M mutation (T790M-mutant group) who were resistant to first-generation EGFR TKIs. In the study, we also investigated sex, smoking status, age at diagnosis, histology, T, N, and M stage, and mutation status. In addition, we analyzed metastatic sites in stage IV patients. RESULTS: Among the EGFR positive-mutant group, 248 (67.95%) patients were stage IV disease. Among them, 41 patients had brain metastases, 86 patients had bone metastases, 16 patients had liver metastases, 168 patients had intrapulmonary metastases, and 39 patients had metastases in other sites. Among the T790M-mutant group, 277 (87.66%) patients were stage IV disease. Among them, 158 patients had brain metastases, 82 patients had bone metastases, 241 patients had liver metastases, 53 patients had intrapulmonary metastases, and 229 patients had metastases in other sites. We also found that lung cancer patients in the T790M-mutant group had higher incidences of the brain (P<0.001), bone (P<0.001), liver (P=0.001), and intrapulmonary metastases (P<0.001). Moreover, wherever the metastatic site was, the metastasis time all centrally distributed in the first two months after diagnosis. CONCLUSIONS: For patients with metastatic lung cancer, most metastases happened before diagnosis, which indicated that metastases related to driving mutations, such as EGFR positive mutation or T790M mutation, but not to the survival time. Lung cancer patients with T790M mutation were more likely to metastasize before the diagnosis.