New evidence indicates that silicone gel breast implants leak more often than thought and that the gel may cause a variety of problems in a recipient's body, government scientists said Tuesday.
It might take years for the leaks to begin, and there is no clear way to determine how many of the estimated 1-million to 2-million American women with implants already have begun to experience "silent" leaks, which have no immediate symptoms, said officials of the Food and Drug Administration (FDA).
Inconclusive evidence points to the possibility that the material may lead to autoimmune diseases and neurological disorders, Alan Andersen, director of the FDA Office of Science and Technology, told a panel of experts that is advising the FDA on scientific questions relating to the implants.
He said the FDA is concerned that early reports of the problem might be the "bellwether" of a looming clinical problem in America.
"An overriding question is what to do about the problem of "silent' ruptures in women who already have these implants," he said.
The scientific panel in November advised the FDA to leave the implants on the market despite lack of evidence the devices are safe. This week it is holding a second round of hearings at the request of FDA commissioner David Kessler.
The panel determined in November that the manufacturers had failed to establish the safety of the devices but recommended that implants remain on the market because of a pressing public health need.
Breast implants have been on the market for three decades. About 150,000 women per year have the surgery _ 80 percent of them for cosmetic reasons, the rest for reconstruction after breast cancer surgery.
Although manufacturers say the devices are safe, Kessler last month called for a voluntary moratorium on further surgery. He said new information, including material from the files of the implants' largest manufacturer, Dow Corning Corp., had raised questions.
Tuesday was the first of three days of testimony on the implants. Representatives of the implant makers will testify and answer questions today; the committee is scheduled to list recommendations Thursday.
Andersen told the advisory panel that the material from Dow Corning's files raised questions about the strength of the solid silicone envelopes that contain the soft, silicone gel which makes up the bulk of each implant.
He then outlined a succession of concerns on which he said FDA officials had sought the panel's advice:
In addition to the danger of rupture, some implants may "bleed," a process in which the gel seeps through tiny openings in the envelope.
Although newer implants contain barriers against gel bleeding, there is evidence that some materials may leak even from these.
The fact that an implant has ruptured or is bleeding may go undetected by the woman or her doctor until she receives X-ray screening for breast cancer. This often would involve more X-ray exposure than a routine mammogram.
Should the implant be removed when a "silent" rupture is discovered? Dow Corning documents indicate the safety of free gel in the body has not been established, and evidence linking the material to conditions such as autoimmune disorders is not conclusive.
In an autoimmune disorder, the body's immune system attacks the body's own tissues.
Researchers testifying Tuesday reported rupture rates about 6 percent and said that figure was probably conservative. Dow Corning officials have said their studies indicate that the number of ruptures never has exceeded 0.5 percent in any year.
Dr. Bernard Patten, a neurologist from the Baylor College of Medicine and one of more than 20 scientists to appear before the panel on Tuesday, predicted an "epidemic" of problems associated with implants, as more and more of them deteriorate over time.
"As time goes by, you're going to see more and more cases," he said.
_ Information from the New York Times and Los Angeles Times was used in this report.