Lung cancer brain metastasis with coma is mostly considered to be caused by intracranial edema, which needs to be treated by radiotherapy, chemotherapy and hypotension. 1. Intracranial edema, brain metastasis of lung cancer, with the increasing volume of tumor, will cause edema and pressure increase in the skull, thus causing coma. Mannitol should be administered intravenously to reduce intracranial pressure and eliminate edema, so as to improve the symptoms of coma; at the same time, radiation therapy should be administered to the lesion area to shrink the tumor. 2. Organ failure, the cancer cells invade the brain nerves and tissues, leading to gradual loss of function and failure, which will also cause coma, for which there is no good treatment for the time being.