Two studies released Tuesday cast further doubt on claims that silicone breast implants cause serious diseases of the body's connective tissues, such as rheumatoid arthritis and fibromyalgia.
A report on the two studies, which were completed in the past year, was released at the annual meeting of the American College of Rheumatology in San Francisco.
The college said: "These studies provide compelling evidence that silicone breast implants expose patients to no demonstrable additional risk for connective tissue or rheumatic disease. Anecdotal evidence should no longer be used to support this relationship in the courts or by the FDA."
Thousands of women have filed lawsuits blaming breast implants for a variety of severe diseases. The Food and Drug Administration has banned most silicone implants except those for women who need breast reconstruction after mastectomies.
But groups that have supported the lawsuits say the studies are not broad enough and the college has spoken too soon.
Dr. Sidney Wolfe with Washington-based Public Citizen said the studies were "grossly over-interpreted." Based on the study results, he argued, there could still be a doubling of cases of arthritis caused by the implants.
One of the studies included research at the University of Calgary in Canada. That study of 1,601 women showed no increased levels of autoantibodies among women with implants. Autoantibodies are present in so-called autoimmune diseases (including those of the connective tissue) in which the body's defenses are turned against the body itself.
Research on 2,304 women at the University of Kansas also showed that women with implants are no more likely to develop fibromyalgia or rheumatoid arthritis than women in the general population.