The concept of lung cancer as a systemic disease has been accepted by everyone, and the treatment paradigm for lung cancer has changed to a multidisciplinary and comprehensive treatment, including surgery, radiotherapy, chemotherapy, immunotherapy, and traditional Chinese medicine. Adjuvant chemotherapy for 4-6 cycles after lung cancer surgery has been carried out in many lung cancer centers nationwide. So, do all lung cancer patients need chemotherapy and/or radiotherapy after surgical resection? The answer is no. If a lung cancer lesion is less than 3 cm in diameter and has no external invasion and no hilar or mediastinal lymph node metastasis, we call it “early stage lung cancer”, or “stage Ia” lung cancer in medical terminology. Clinical trials have proved that chemotherapy after surgery for stage Ia non-small cell lung cancer patients not only cannot prolong life, but also shorten survival due to toxic side effects of chemotherapy. Therefore, adjuvant chemotherapy is not needed for patients with stage Ia lung cancer after surgery. In addition, adjuvant chemotherapy after surgery for elderly lung cancer patients aged 75 years or older also cannot improve the survival rate. This is because elderly patients have different degrees of declining physical functions and cannot easily recover from the bone marrow suppression and gastrointestinal reactions caused by chemotherapy. Lung cancer is a systemic disease, not just a disease of the lungs. Surgery only solves the most prominent problems of the lung, but the problems of the whole body can only be solved by chemotherapy, etc. For the sporadic cancer cells that walk the whole body, postoperative adjuvant chemotherapy can kill them, and the patient can survive longer. It has been proved that postoperative adjuvant chemotherapy for lung cancer is beneficial to improve the survival rate of lung cancer, especially for patients in the middle and late stages. It should be noted that postoperative adjuvant chemotherapy for lung cancer is a highly specialized task, which not all doctors are competent to perform. It is not advisable for patients to bring their own chemotherapy regimen and may bring negative effects.