Answers
03/22/1993
IMMUNOLOGY STUDIES ON SILICONE GEL
T93-15 Susan Cruzan
March 22, l993 (301) 443-3285
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 antibody 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). These studies
in rats used a cow's blood protein, bovine albumen, as the antigen. The
following can be used to answer questions.
FDA believes that these studies help provide a scientific understanding
for the possible link between silicone gel-filled breast implants and
autoimmune-like disorders. However, the studies do not establish the
connection with certainty, particularly since they were designed to
intentionally stimulate an antibody 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 under way.
In the two 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, silicone gel was blended with liquid silicone
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and a known antigen and injected into the rats. Under these test conditions,
the antigen alone would not have been expected to produce an immune response.
In the presence of silicone gel or another adjuvant, however, it produced a
strong antibody response. The study by Dr. Naim is being published on March
22 in the journal Immunological Investigations.
FDA has been concerned for a long time that silicone gel might provoke an
immune response in at least some women. That is one of the reasons the agency
decided to restrict the availability of these devices. These new studies are
consistent with this concern, although they certainly do not prove the
implants cause immune-related disorders.
Based on these studies, FDA will require breast implant manufacturers to
update information about the possible connection between the implants and
immune-related disorders in the informed consent documents for women receiving
breast implants under clinical studies.
The symptoms of the immune system 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. Many women with or without breast implants have one or
more of these symptoms from time to time. However, people who have
immune-related disorders, which are relatively rare, generally experience a
combination of these and other symptoms that don't go away as they do for
those without such disorders.
The 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 doctor if the symptoms
don't subside. These complaints could be indicators of a variety of health
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problems, not just immune-related disorders. Depending on the situation, a
woman's doctor may refer her to a rheumatologist or other
type of specialist for further evaluation.
Questions have also been raised about whether the new studies addressed
the safety of other types of implants made with silicone. There are many
different materials known as "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.