CHICAGO (Reuters) - Popular rheumatoid arthritis drugs that block a protein linked with inflammation do not appear to raise the overall risk of cancer, Spanish researchers said on Saturday.
The drugs, known as TNF blockers, suppress the immune system by blocking the activity of an inflammatory protein called tumor necrosis factor, or TNF.
They have been used since 1998, but some studies have suggested the drugs raise the risk of cancer -- particularly lung cancer and lymphoma -- by toning down the immune system.
"Despite foreseen fears, blocking the tumor necrosis factor does not make patients more prone to develop cancer," Dr. Loreto Carmona of the Fundacion Espanola de Reumatologia in Madrid said in a statement.
Carmona, who is presenting his research at the American College of Rheumatology's annual meeting in San Francisco, used health data collected from two Spanish registries -- databases of patients.
One included nearly 4,500 people taking the drugs from 2001 through 2007; while the other included data from 1999 through 2005 on nearly 800 people with RA not taking the drugs.
Overall, the researchers found 70 cases of cancer in the group that took the drugs, compared with 29 cases in the group that did not take the drugs.
Because the groups were of different sizes and followed for different periods of time, they did a calculation that showed no statistical difference in the cancer risk between the two groups.
Dr. Eric Matteson of the Mayo Clinic in Rochester, Minnesota, who was not part of the research, said the findings offer some assurances. "What it tells us is if there is an increased risk of cancer, the overall event rate is still very low," he said in a telephone interview.
But he said the study has several limitations, the main one being that people in the studies were not matched ahead of time for age, sex, and other health problems.
And while the study looked at the overall risk for cancer, Matteson said it did not address whether there is an increased risk of specific types of cancer.
Nor does it address whether the drugs might pose a particular threat to children and teens, something the U.S. Food and Drug Administration is currently investigating.
"Overall, there doesn't seem to be a higher risk of cancer, but these assessment tools are still imperfect," Matteson said. "The FDA and physicians and doctors are still concerned and that is why there are warnings for all of these drugs on the package label about concerns over cancer."
Anti-TNF drugs include Johnson & Johnson's Remicade or infliximab, Abbott Laboratories Inc's Humira or adalimumab, Amgen Inc and Wyeth's Enbrel or etanercept and UCB's Cimzia or certolizumab pegol.
Rheumatoid arthritis is an autoimmune disease and often strikes young people, resulting in pain, stiffness and swelling. It affects about 20 million people worldwide.
Editing by Maggie Fox and Eric Beech