For intermediate to advanced non-small cell lung cancer, chemotherapy and targeted drug therapy are the main systemic treatments. According to the latest international general guidelines, patients should first be tested for EGFR gene mutations in various pathological cytology specimens, and patients with positive mutations are first recommended to be treated with targeted agents, while negative patients are treated with chemotherapy in the first line. When the lesions in the lung increase to a certain size or new lesions appear, the first-line treatment strategy is judged to have failed and second-line treatment is given at this time. However, in some patients with stable lesion size but no improvement in symptoms, if there is evidence that the lesion is still very active, first-line therapy may be terminated early and the treatment strategy changed. Case 1: A 60-year-old female with adenocarcinoma of the right lung with massive malignant pleural effusion and irregular pleural thickening, starting with chest tightness and chest pain. The patient was given pemetrexed combined with cisplatin chemotherapy for 3 segments in the first line, and the size of the intrapulmonary lesion was stable. However, the patient complained that the symptoms of chest tightness and chest pain had not been reduced and had a tendency to worsen. The FDG isotope scan of the lung was reviewed, which indicated that the intrapulmonary lesions and thickened pleural activity were strongly positive and higher than before treatment, suggesting active tumor cell growth and metabolism. After 1 week, the patient’s chest pain and chest tightness improved significantly. After one week, the patient’s chest pain and chest tightness improved significantly. The patient’s general condition was good, no more chest pain and chest tightness. The patient has been taking the medication for 8 months, the efficacy is still stable and the general condition of the patient is good. Experience summary: 1. According to the basis that the patient’s complaints did not improve and the tumor activity increased after chemotherapy, the treatment strategy was changed in time. At this time, according to the international RECIST criteria, the patient should still undergo first-line chemotherapy. 2. This patient was negative for EGFR gene mutation testing, but taking EGFR-TKI was still effective. Therefore, it is suggested that even for patients with negative EGFR mutation test, targeted drug therapy should still be tried. Case 2: The patient is a 40-year-old female with adenocarcinoma of the right upper lung with cancerous pleural fluid. The pleural fluid test was positive for EGFR mutation. However, the patient did not know enough about targeted drugs and refused to take them in the first line. Therefore, pemetrexed combined with cisplatin chemotherapy was given for 2 segments, and the lesion did not shrink significantly. Isotope FDG lung scan showed high activity of the lesion in the lung, and the patient felt no reduction of chest pain symptoms. The patient was given a change in treatment strategy, stopping chemotherapy to take targeted drugs, and the lesion shrank significantly after one month, and the isotope FDG lung scan showed no significant activity of the lesion after 3 months. Experience summary: 1. Patients should strengthen their knowledge of targeted drugs, and those with positive EGFR gene mutations should try to use EGFR-TKIs in the first line. 2. Treatment for patients should be individualized, not only according to the principles of treatment, but also according to the specific situation and flexible timing of treatment strategy change, otherwise the best time for change will be missed. In conclusion, if conditions are available, PET-CT can be used to determine the changes of tumor activity, so as to guide the treatment. If conditions are limited, isotope FDG lung scan, which is reimbursable by medical insurance, can be used to help determine the effect of treatment, thus making up for the shortcomings of the traditional RECIST method (which only measures changes in lesion size to determine the effect of treatment) and truly individualizing the treatment of lung cancer patients.