There is no such thing as the most difficult type of lung cancer to treat, relatively speaking, small cell lung cancer is more difficult to treat. Clinically, lung cancer can be categorized into small-cell lung cancer and non-small-cell lung cancer according to its pathology. Small cell lung cancer is characterized by rapid progression, high malignancy, easy recurrence, and difficult treatment, and it is the more difficult type of lung cancer to treat at present. According to the results of a meta-analysis of 94,703 NSCLC patients reported in the AJCC 8th Edition Tumor Staging Manual 2017: the 5-year survival rate for patients with Stage I SCLC is about 50%; for Stage II, it is about 25%; for Stage III, it drops to about 10%; and for Stage IV, it is less than 3%. If a patient is diagnosed with small cell lung cancer, a combination of chemotherapy, radiotherapy, surgery and other therapeutic measures may be needed to inhibit the growth and reproduction of malignant cells as much as possible, to reduce the recurrence rate of the cancer, and to prolong the survival time of the patient as much as possible.