The absence of mutations in the genes of patients with brain metastases from lung adenocarcinoma is usually due to the absence of mutagenic factors for gene mutation. Mutagenesis of gene mutation includes physical mutation, chemical mutation and biological mutation. The purpose of lung adenocarcinoma genetic testing is to decide whether patients can use targeted drugs or not. 1. Physical mutation: including X-ray, a-ray, ionizing radiation, etc. can lead to gene mutation in cancer patients. 2. Chemical mutagenesis: including metal ions, alkaloids, antibiotics, pesticides, etc. can induce gene mutation. 3. Biological mutation: including bacteria, virus, mold, etc. can cause gene mutation in cancer patients. Lung adenocarcinoma brain metastasis patients without these gene mutation triggers usually will not lead to gene mutation. If no mutation is found in the patient’s genetic test, it means that the targeted therapeutic drugs with good therapeutic effect are not applicable to the patient, and the patient can only be treated with other therapeutic methods such as chemotherapy or immunotherapy. Patients with brain metastasis of lung adenocarcinoma should actively consult the doctor, and they should not treat themselves, but make individualized treatment plan and follow the standard treatment under the guidance of doctor’s consultation.