The findings should reassure patients who take Enbrel, Remicade, or Humira. All of these drugs are so-called biologics -- meaning they are derived from living organisms. They are known as necrosis factor (TNF)-blocking biologics.
"If there is a [cancer] risk, this study supports the conclusion that it is a small one," says researcher Soko Setoguchi, MD, DrPh, of Harvard Medical School's Brigham and Women's Hospital.
Lymphoma Risk Well Known
Rheumatoid arthritis patients do have a higher than normal risk for developing certain cancers, especially cancers known as lymphomas.
But it has been unclear if this elevated risk is due to the disease itself, or to the drugs used to treat it.
Studies examining the highly effective TNF-blocking drugs have been mixed. A widely-reported analysis by researchers from the Mayo Clinic published late last spring found a threefold increase in cancer risk among patients who took Remicade and Humira. That analysis didn't look at Enbrel.
The Mayo Clinic research weighed data from nine studies that compared biologic treatments to placebo.
In the newly published study, Setoguchi and colleagues compared the biologic drugs to the traditional rheumatoid arthritis drug, methotrexate.
Drugs like methotrexate are known as disease-modifying antirheumatic drugs. They slow down rheumatoid arthritis and improve quality of life for most people.
In the Harvard study, 1,152 patients took a TNF-blocking biologic, while 7,306 took methotrexate.
The patients were all 65 or older. They were identified through insurance databases in New Jersey, Pennsylvania, and British Columbia, Canada.
Even though the biologic users tended to have more severe rheumatoid arthritis than those who took methotrexate, the researchers found no significant difference in cancer risk between the two groups.
The biologic users were followed for an average of 2.6 years, compared to 4.2 years for patients taking methotrexate. Setoguchi tells WebMD the researchers will continue to follow study subjects.
"We will need longer follow-up with a larger number of patients to provide precise answers," she says. "Until then, this issue [cancer risk] should be part of the decision-making process for patients who consider taking these drugs."
Inflammation and Cancer
Dallas rheumatologist John J. Cush, MD, tells WebMD that rather than increasing cancer risk, TNF-blocking drugs may actually lower it, as well as the risk for other diseases, because the drugs target inflammation.
Rheumatoid arthritis is a degenerative autoimmune disease caused by chronic inflammation. It is most commonly associated with the joints, but it can affect other areas of the body as well.
Meanwhile, inflammation has also been implicated as a possible cause of certain cancers, and even heart disease.
"A question that is just as important as 'What is the risk of this therapy?' is 'What is the risk of this disease?'" says Cush, chief of rheumatology and clinical immunology at Presbyterian Hospital, Dallas.
"Depending on how you view the studies, there is either no risk or a marginally increased risk of lymphoma associated with taking these drugs," he says. "But we know that they have a dramatic impact on quality of life for many rheumatoid arthritis patients who are disabled by the disease."
SOURCES: Setoguchi, S. Arthritis and Rheumatism, September 2004; vol 54: pp 2757-2764. Soko Setoguchi, MD, DrPh, instructor of medicine, Brigham and Women's Hospital, Harvard Medical School. WebMD Medical News: "Arthritis Drugs May Up Cancer Risk." John J. Cush, MD, chief of rheumatology and clinical immunology, Presbyterian Hospital, Dallas.
By Salynn Boyles
Reviewed by Louise Chang