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In cancer treatment, chemotherapy refers to particular drugs used to kill or slow the reproduction of rapidly multiplying cells. In rheumatology, chemotherapy is designed to decrease the abnormal behavior of cells, rather than kill 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; for example - causing painful joints as in rheumatoid arthritis. In many cases, inflammation results from autoimmunity, a malfunction of the immune system where one's own tissues or organs are not recognized as such and are attacked by the body's immune system.

Chemotherapy helps people with certain inflammatory and autoimmune diseases because it slows cell reproduction and decreases certain products made by these cells that cause an inflammatory response to occur.

What Chemotherapy Drugs Are Used to Treat Rheumatic Diseases?

Although there are many chemotherapy drugs, only a handful are used to treat rheumatic diseases today. These are:

• Methotrexate (Rheumatrex, Trexall) is the chemotherapeutic drug most widely used by rheumatologists because it is effective in treating rheumatoid arthritis and certain other rheumatic diseases (such as certain forms of vasculitis, an inflammatory disease involving the blood vessels), and it is relatively safe. Most patients can take methotrexate by mouth in a single, weekly dose. Some patients prefer to take it as an injection once a week.

• Imuran. Imuran has been used for many years as an immunosuppressive drug to prevent organ rejection in patients receiving kidney transplants. Usually taken in a single daily dose by mouth, Imuran also is used to suppress the abnormal immune response in some patients with vasculitis, systemic lupus erythematosus (lupus) and, less often, rheumatoid arthritis.

• Cytoxan. Cytoxan is considerably more powerful and has more side effects than methotrexate and Imuran. It is used to treat the more severe, life-threatening or organ-threatening rheumatic diseases, such as severe systemic lupus erythematosus and some forms of vasculitis. This drug, taken either by mouth or injection, directly attacks the parts of the cell nucleus that contain the genes interfering with the production of certain proteins. These proteins (antibodies) are involved with the autoimmune response. Although rapidly reproducing cells are more susceptible to this action than resting cells, any cell in the body can be affected if there is enough of the drug present.

• Arava. Arava helps calm the inflammation associated with rheumatoid arthritis by inhibiting production of inflammatory cells. It is taken by mouth once daily.

• CellCept. CellCept has been used to treat people with autoimmune conditions including lupus and some forms of vasculitis. It works by impairing the function of immune system cells that become overactive in autoimmune diseases. It is taken by mouth twice daily.

Side effects of chemotherapeutic drugs are fairly common, even though the doses are typically lower than the doses used to treat cancer.

All of these drugs can suppress the formation of blood cells, resulting in:

• Anemia or low red blood cell count. Red blood cells are the cells that carry oxygen throughout your body
• Leukopenia/Neutropenia or low white blood cell count that may cause decreased ability to fight infection
• Thrombocytopenia or low platelet count that may cause impaired blood clotting

Women who are pregnant, or who plan to become pregnant, should not use these medications.

The elderly and those with other chronic medical conditions may experience more side effects and a dosage adjustment may be necessary.

Since no drug is entirely safe, your doctor 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.

It is very important to have the appropriate follow-up examinations and laboratory testing while taking chemotherapeutic drugs. Careful monitoring can minimize all of these risks.

How Long Does Treatment Last?

Although there are some differences among the 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. Generally, if there is no benefit within four months, it is unlikely that continuing the chemotherapeutic drug at the same dose will be helpful.

Methotrexate and Imuran can be used for prolonged periods (many years) if necessary, as long as they do not cause side effects. Cytoxan is generally used for more limited periods because of its greater side effects. However, in certain cases more prolonged use may be necessary.

Get support. Check out resources for people with arthritis.
Learn about other arthritis medicines.
View the full table of contents for the Arthritis Guide.
Reviewed by the doctors at The Cleveland Clinic Department of Rheumatic and Immunologic Diseases (2006).

Edited by Cynthia Haines, MD, WebMD, May 2006.
SOURCE: American College of Rheumatology