Gemcitabine carries a risk of radiation sensitization and severe pulmonary and esophageal fibroid degeneration when combined with radiation therapy. Gemcitabine is used as a first-line application in locally advanced and already metastatic non-small cell lung cancer; secondly, gemcitabine is a second-line agent for patients with advanced pancreatic cancer after failure of fluorouracil-based therapy, which improves patients’ quality of life. Gemcitabine alone does not cause pulmonary fibrosis; when gemcitabine is used in combination with radiation therapy, there is a risk of radiation sensitization and severe pulmonary and esophageal fibroid degeneration. ADVERSE REACTIONS WITH Gemcitabine: The dose-limiting toxicity of this product is myelosuppression, which is more common for both neutrophils and platelets. Mild to moderate gastrointestinal reactions such as diarrhea, constipation, and stomatitis. Fever, rash and flu-like symptoms may also be caused. A few patients may have hematuria, proteinuria, abnormal liver and kidney function, and dyspnea. Precautions for the use of gemcitabine: Increasing the frequency of dosing and prolonging the duration of titration of the drug can increase the toxicity of the drug. The dose should be appropriately reduced in elderly patients. Intervals with radiation therapy should be at least 4 weeks, or shorter if the patient’s condition permits. Contraindications to the use of gemcitabine: It is contraindicated for those who are allergic to the product. The combined use of this product and cisplatin is contraindicated in patients with severe renal insufficiency. It is contraindicated in pregnant and lactating women. The above drugs need to be standardized and rationally applied under the guidance of professional physicians and pharmacists. If the symptoms fail to improve or even gradually aggravate, it is necessary to consult a regular hospital in time, and cooperate with the doctor to improve the examination and standardize the treatment.