In rheumatology, chemotherapy is designed to alter the abnormal behavior of cells. The doses of medication used for rheumatic or autoimmune conditions are lower than the doses used for cancer treatment.
How Does Chemotherapy Treat Inflammatory and Autoimmune Diseases?
In many rheumatic diseases, inflammation causes damage to parts of the body, such as what happens to the joints in rheumatoid arthritis. In many cases, inflammation results from autoimmunity, a malfunction of the immune system in which a person's own tissues or organs are mistakenly attacked by the body's immune system.
Chemotherapy slows cell reproduction and decreases certain products made by these cells. Therefore it may help people with certain inflammatory and autoimmune diseases. Because of the suppressive effect of chemotherapy on autoimmunity, these drugs are sometimes called immunosuppressive drugs.
What Chemotherapy Drugs Do Doctors Use?
Although there are many chemotherapy drugs, only three are widely used in treating rheumatic diseases today. These are:
Methotrexate is the chemotherapeutic drug most widely used by rheumatologists for two main reasons: It is effective in treating rheumatoid arthritis and certain other rheumatic diseases (especially polymyositis and certain types of vasculitis or inflammation of blood vessels), and it is relatively safe.
Most people can take methotrexate by mouth in a single, weekly dose. Some patients prefer to take it as an injection once a week.
Azathioprine has been used for many years as an immunosuppressive drug to prevent rejection in patients receiving kidney transplants. It is also used to suppress the abnormal immune response in some patients with vasculitis, systemic lupus erythematosus, rheumatoid arthritis, and vasculitis. Azathioprine has been linked to lymphoma, a cancer of the lymph nodes.
Cyclophosphamide is considerably more powerful and toxic than methotrexate and azathioprine. It is used to treat the most aggressive and dangerous rheumatic diseases, such as severe lupus and some forms of vasculitis.
Cyclophosphamide directly attacks rapidly reproducing cells such as those in the immune system. Resting cells, that are not multiplying, can be affected if there is enough drug present. It is taken either by mouth or by injection.
What Are the Side Effects of Chemotherapy Drugs?
All of these drugs can suppress the formation of blood cells, resulting in the following:
- Anemia: low red blood cell count
- Leukopenia/Neutropenia: low white blood cell count that may cause decreased resistance to infection
- Thrombocytopenia: low platelet count that may cause impaired blood clotting
In addition, methotrexate and azathioprine can damage the liver, and cyclophosphamide can damage the urinary bladder lining and cause bleeding or cancer in the bladder lining. Cyclophosphamide also causes hair loss and sterility.
Methotrexate and cyclophosphamide can damage the lungs.
Because no drug is entirely safe, your rheumatologist will talk to you about the possible benefits of these drugs, as well as their side effects. The occurrence of side effects depends on the dose, type of medication, and length of treatment.
Obviously, it is very important to have the appropriate follow-up exams and laboratory testing while taking chemotherapy drugs. Careful monitoring can minimize all of these risks.
How Fast Do Chemotherapy Drugs Work?
Although there are some differences among chemotherapy drugs and how they are used to treat certain rheumatologic and autoimmune diseases, these drugs usually produce benefits gradually, requiring weeks to months for full effectiveness.
Methotrexate and azathioprine can be used for prolonged periods (many years) if necessary, as long as they do not cause side effects.
Cyclophosphamide is generally used for more limited periods because of its greater toxicity. However, in certain cases, more prolonged use may be necessary. However, if there is no benefit within four months, it is unlikely that continuing the same dose will be helpful.