Rheumatologists and oncologists often use methotrexate, cyclophosphamide and other drugs, which are often referred to as “chemotherapy drugs” by the general public. Oncology patients often experience hair loss and other side effects after chemotherapy, so when rheumatologists prescribe these drugs to patients, it often makes them suspicious. In fact, weighing the pros and cons, in many cases, it is necessary to use “chemotherapy drugs” for rheumatology patients. Let’s explore the reasons for this. First of all, it is necessary to introduce the concept that rheumatic disease is a general term for a large group of diseases, including many independent diseases, such as rheumatoid arthritis, systemic lupus erythematosus, dry syndrome, systemic vasculitis, etc. Most of them are caused by problems with the immune function of the human body. It is important to emphasize that the immune function problem here is not what we usually call “immune deficiency”, but rather immune dysfunction or “hyperimmune function”. Under normal circumstances, our immune system is like a guard to protect the body from germs, but when rheumatic diseases occur, these “guards” begin to become “fully armed” and “indistinguishable from the enemy “This is the cause of rheumatic diseases. Tumor is a malignant disease, and the principle of tumor treatment is “either one or the other”. The abnormal growth of a certain part of the patient’s body excessively consumes the nutrients needed to maintain the body on a daily basis, thus leading to the failure of the body. Therefore, tumor treatment often uses drugs that have a killing effect on body tissues, and in addition to methotrexate and cyclophosphamide, a variety of drugs that have a killing effect on cells are used in combination. For example, methotrexate is used to treat lung tumors at a dose of about 40-50 mg. With high doses, adverse reactions are inevitable. Rheumatic diseases are not malignant diseases, but chronic inflammatory diseases. The main purpose of rheumatic disease treatment is: to adjust the body’s disordered immune system and suppress the overactive immune function. Since methotrexate, cyclophosphamide and other drugs have very good immunomodulatory effects, they are often used in the treatment of rheumatic diseases, but the dosage and application methods are very different from those for tumors. Rheumatic diseases are highly individualized, and doctors choose different drugs depending on the type of disease and the severity of the symptoms, which are generally much milder than tumor treatment. Again, the dosage of methotrexate in the treatment of rheumatoid arthritis is usually 10mg to 15mg once a week, which is much lower than the dosage for tumor treatment. The treatment of rheumatic diseases is often a long-term process, and careful monitoring and conditioning is required during treatment. Any drug has side effects, and patients often do not follow medical advice because of concerns about drug side effects. In fact, the benefits of drug therapy far outweigh the side effects. For example, for some diseases, patients survive for less than two years without the use of hormones and cyclophosphamide, while their use allows most patients to survive for a long time. Patients with rheumatoid arthritis typically develop joint deformities within two years without the use of immunomodulators, while methotrexate can effectively prevent disability. Common side effects of the above drugs include elevated transaminases, blood in the urine, and anemia, which usually do not cause serious problems under close monitoring by a doctor. Unlike tumors, many patients with rheumatic diseases need and should be treated with methotrexate, cyclophosphamide and other drugs. Long-term clinical practice has confirmed that methotrexate and other drugs are not only safe and effective but also economical in treating rheumatic diseases, which can reduce patients’ pain, control the progress of diseases and improve their quality of life. It is important that patients need to use the drugs in a standardized and reasonable manner under the guidance of rheumatologists.