DRAFT
                                March 18, 1993

FDA TALK PAPER:

NEW IMMUNOLOGY STUDIES ON SILICONE GEL

Two recent animal studies have shown that silicone gel of the type used in breast implants can act as an immune system adjuvant. That is, it can enhance the ability of the animals’ immune systems to produce antibodies to an antigen (a substance that stimulates the body to produce antibodies).

FDA believes that these studies confirm the possibility that there may be a link between silicone gel—filled breast implants and autoimmune-like disorders, but the studies do not establish the connection with certainty, particularly since they were designed to intentionally stimulate the immune response by mixing a known antigen with the silicone. More research will be needed before the relevance of these studies to women with breast implants can be established. Some of this research is already underway.

The two new studies —— one conducted in New York state by Dr. John Naim and his colleagues and the other by Dow Corning Corporation, a supplier of silicone gel for implants, show for the first time that silicone gel can act as an adjuvant. (A study in 1974 had shown that some of the chemical constituents of silicone gel have adjuvant properties.) In the new studies, silicone gel was blended with liquid silicone and a known antigen and injected into the animals. The antigen alone would have been expected to produce an immune response, but the immune response was strongly increased by the silicone gel. The study by Dr. Naim will be published on March 22 in the journal Immunological Investigations.

Responding to the studies, FDA Commissioner David A. Kessler said, “We’ve been concerned for a long time that silicone gel might provoke an immune response in at least some women. That’s one of the reasons we decided to restrict the availability of these devices. These new studies are consistent with that concern, although they certainly don’t prove the implants can cause immune—related disorders.”

Based on these studies, FDA will require breast implant manufacturers to add information about the possible connection between the implants and immune-related disorders to the informed consent documents for women receiving breast implants under clinical studies.

FDA’s advice to women who already have the implants remains the same as in the past. The agency recommends that any woman with implants be alert to the symptoms of these disorders, and that she consult her regular doctor if she has symptoms that don’t subside. These complaints could be indicators of a variety of health problems, not just immune-related disorders. Depending on the situation, her doctor may refer her to a rheumatologist or other type of specialist for further evaluation.

The symptoms of these disorders include pain and swelling of joints; tightness, redness or swelling of the skin; swollen glands or lymph nodes; unusual and unexplained fatigue; swelling of the hands and feet; and unusual hair loss. People who have immune-related disorders, which are relatively rare, generally experience a combination of these and other symptoms.

Questions have also been raised about whether the new studies addressed the safety of other types of implants made with silicone. Most of the silicone used in a variety of implanted devices, such as shunts, catheters, artificial joints and facial implants, consists of relatively hard silicone elastomer (“silicone rubber”) rather than gel. Silicone rubber was not investigated in these studies, and there is no evidence to date that it has immune system adjuvant properties.