The survival of patients with mid-stage lung cancer without treatment depends on the metastatic site, pathological type and their own physical condition, as follows: 1. Patients with mid-stage lung cancer usually have metastatic lesions, and if they have brain metastases and the metastatic site is in the brain stem, these patients with advanced lung cancer will live for a very short time, even less than a month, because they will die quickly from brain herniation caused by tumor compression of brain tissue.2. Patients with mid-stage lung cancer with only regional lymph node metastasis, who are in good physical condition and have fewer comorbidities, may live for about one year even without treatment.3. The type of pathology is also an important factor in determining the survival period of lung cancer patients, the survival period of small cell lung cancer patients is significantly shorter than that of non-small cell lung cancer, and the survival period of patients with mid-stage small cell lung cancer is generally shorter than The survival period is generally shorter than three months. In conclusion, it is difficult to generalize the natural course of lung cancer patients without treatment, which is affected by many factors and should be considered in a comprehensive manner.