When headache occurs in patients with advanced lung cancer, the main reasons may be as follows: I. Brain metastasis: this is the most common reason, brain is one of the common metastatic target organs of lung cancer, and patients with advanced lung cancer, especially those with small-cell lung cancer, have a high risk of brain metastasis. Brain metastasis can compress brain nerves, and headache, dizziness and other symptoms can appear in the early stage of the disease. Severe anemia: patients with advanced lung cancer may suffer from severe anemia due to severe malnutrition or bone marrow suppression after chemotherapy, which may cause patients to suffer from dizziness and headache. Respiratory failure: lung function of advanced lung cancer patients is seriously impaired, and respiratory failure may occur, leading to acidosis, carbon dioxide retention, electrolyte disorder and other complications, inducing headache, dizziness, vomiting and other symptoms. Lung infection: patients with advanced lung cancer have poor immunity, and the lung tumor leads to poor sputum discharge from bronchial tubes, so the chance of lung infection is very high. Patients may suffer from hypoxia due to severe lung infection, which may lead to dizziness, headache and other symptoms.