Lung cancer fever in the afternoon may be a manifestation of infection, reabsorption fever and cancer fever. 1. Infection: the immunity of lung cancer patients is relatively low, and the defense ability of lungs will be reduced, which is likely to be combined with bacterial or viral infection of lungs, and when this happens, fever symptoms may appear in the afternoon. 2. Reabsorption fever: the diseased tissues of lung cancer may have infiltrative growth to the surrounding area, and a large amount of pleural effusion may appear, which will be gradually absorbed by the pleural tissues, and in the process of absorption, fever may also appear, and it will occur in the afternoon in most cases. 3. Cancer fever: lung cancer tissues will secrete and produce a large amount of toxin substances, after these substances enter into the blood, they may also cause the rise of body temperature, which leads to fever in the afternoon of lung cancer patients. When lung cancer patients have fever, they need to actively replenish water and vitamins, and at the same time take effective treatment measures as early as possible, only when the condition is under stable control can the fever in the afternoon be improved.