THURSDAY, Aug. 31, 2006 (HealthDay News) -- Concerns that rheumatoid arthritis drugs called TNF blockers and related medications could cause cancer appear to be unfounded, a new study shows.
Rheumatoid arthritis sufferers do tend to have higher rates of cancer than people without the autoimmune illness. But a team of U.S. and Canadian researchers found no increased risk for cancer among patients using drugs such as TNF blockers compared to those using other medications.
However, cancer can develop over decades, and the drugs in question have only been around for a few years, the experts noted. They also said it's difficult to determine what's driving the higher rates of cancer seen in rheumatoid arthritis patients -- the drugs they take or the illness itself.
In any case, medications such as tumor necrosis factor (TNF) antagonists remain "amazing drugs" for easing arthritis symptoms, said Dr. Harminder Sikand, a pharmacist at Scripps Mercy Hospital in San Diego. She was not involved in this study.
TNF blockers include infliximab (Remicade), etanercept (Enbrel), and adalimumab (Humira). The drugs work by dampening down the immune system, which becomes hyperactive in patients with rheumatoid arthritis.
An estimated two million Americans have the disorder, where chronic inflammation leads to joint damage, pain, and stiffness.
Scientists have long noticed a connection between cancer -- especially leukemias and lymphomas -- and autoimmune diseases like rheumatoid arthritis, explained another expert, Dr. Clifton O. Bingham III, assistant professor of medicine at the Johns Hopkins University Arthritis Center.
But the reasons behind the arthritis-cancer link have remained unclear, Bingham said. One prevalent theory: Anti-arthritis drugs like TNF blockers might allow cancer to occur because they suppress the immune system's ability to fight off tumors.
"When we think we come in with these [pharmaceutical] magic bullets, we may be knocking out something that we need," Bingham said.
Earlier this year, a review of research suggested that the risk of cancer was 3.3 times higher in patients who took TNF-blockers compared to those taking a placebo. The overall risk of any one patient developing cancer remained very small, however.
According to that review, 154 people would need to be treated with one of the drugs for each single person who would go on to develop cancer within six to 12 months.
In the new study, researchers from Harvard Medical School, Boston, and the University of British Columbia, in Vancouver, examined the medical records of 1,152 people who took TNF-blockers or a related drug called anakinra (Kineret), as well as 7,306 who took another rheumatoid arthritis drug, methotrexate (brand named Rheumatrex and Trexall).
An estimated 70 percent of rheumatoid arthritis patients are on methotrexate, Bingham said.
Reporting in the September issue of Arthritis & Rheumatism, the researchers concluded that users of TNF-blockers and related medications are "unlikely" to have a significantly higher risk of cancer than those who take methotrexate.
While the study results are encouraging, Bingham said they aren't the "final word" on the subject.
It's possible that longer-term studies may still reveal higher cancer rates, said Bingham, who's received funding from companies that are developing TNF blockers.
What should patients do? Sikand, the pharmacist, suggested they consider the potential costs and benefits of the drugs.
The benefits can be great, Sikand said. "For those who are afflicted by this disease, these drugs have changed their lives. They're able to have a normal life."
More information
To learn more about rheumatoid arthritis, visit the Arthritis Foundation.
