Back pain after taking targeted drugs for lung cancer may be caused by physiological factors, adverse reaction of targeted drugs and tumor bone metastasis. 1. Physiological factors: fatigue injury of shoulder and back muscles due to bad posture or excessive exercise may cause back pain, which can be relieved by rest and local hot compress. 2. Adverse reaction of targeted drugs: Targeted drugs can kill cancer cells and damage normal cells at the same time, and the muscle or bone tissue of the back can also be affected by targeted drugs, which can cause back pain, and the patients need to adjust the dosage of drugs or change other drugs under the guidance of doctors. 3. Tumor bone metastasis: Due to the lack of obvious efficacy of targeted drug treatment, bone metastasis occurs in the tumor. When the tumor metastasizes to thoracic vertebrae and scapula, it will cause bone destruction and back pain. After taking targeted drugs for lung cancer, back pain symptoms should go to the hospital in time to improve the examination, clarify the cause of the disease, and carry out targeted treatment according to the cause of the disease.