By GARDINER HARRIS
WASHINGTON, April 6 - In documents made public on Wednesday, health regulators estimated that up to 93 percent of silicone breast implants ruptured within 10 years. The surprisingly high figure will further roil a debate next week about whether to lift the 13-year-old ban on silicone implants for breast enhancement.
A committee of plastic surgeons and other experts will convene on Monday to sort through studies of the safety and resilience of silicone implants. The panel is also widely expected to hear emotional testimony from scores of women who have had the implants.
The experts are to decide by April 13, the last day of the hearings, whether the implants are safe enough to be approved for wide use. The Food and Drug Administration then decides whether to follow the recommendation.
The panel voted, 9 to 6, in October 2003 to approve silicone implants. In an unusual move, its chairman later wrote a letter to the F.D.A. urging that it reject the recommendation. The agency sided with the chairman and ruled that more information was needed about long-term safety.
The crucial issues are how often the implants break, what happens to the silicone when they rupture and what health effects result. In the late 1980's and early 90's, thousands of women said ruptured implants had caused myriad connective-tissue and autoimmune diseases that included multiple sclerosis. The assertions bankrupted Dow Corning, a large maker of implants.
An expert committee of scientists found in 1999 that there was little evidence that silicone implants caused such diseases. Instead, the primary safety concern, the panel found, was the tendency of silicone implants to cause local complications like infections, pain and scarring.
Critics have continued to insist that silicone implants are dangerous. Organizations of plastic surgeons and companies like Inamed and Mentor that make implants contend just as vigorously that they are safe.
Underlying the scientific issues are deeply emotional questions about self-image. Physicians are allowed to use silicone implants for women who need reconstructive surgery after major illnesses like cancer. Broader approval would most likely accelerate the growing popularity of breast-enhancement operations.
Some advocates believe such operations should be discouraged. Others say larger breasts can provide women with important help for self-esteem.
The panel will not resolve this debate. Its task is to assess safety, and that will be hard enough. The F.D.A. provided the panel with wildly varying estimates of just how often implants rupture.
Inamed studied its implants for four years and found that 9 percent a year rupture. Those numbers are fraught, however, because most patients have no idea when their implants rupture, and imaging tests are accurate in assessing failures only about two-thirds of the time.
Projecting the numbers over 10 years called for even more guesses. If one assumes that implants are no more likely to fail in their 10th year as they are in their first, just 21 percent of a cross-section of women will see their implants fail in 10 years.
But in comments posted on Wednesday on the agency's Web site, reviewers wrote that implants, like cars and hearts, are more likely to fail as they age. Adjusting for the increasing risks that come with age, the agency estimated that 74 percent of a cross-section of women would suffer implant failures in 10 years. For women undergoing reconstructive surgery, mostly breast cancer survivors , the failure rate is 93 percent.
Saline implants fail, too, but such failures are quickly recognized by women as their breasts deflate. And there is little risk associated with saline seepage.
The risks of silicone seepage are not fully known, however. Scar tissue generally forms around most implants, but silicone leaks out of the scar pocket in about one-fourth of patients, the agency found. Because most failures of silicone implants go unrecognized, the agency suggested that women with them should undergo medical screening every year or two.
Dr. Mark Jewell, president elect of the American Society of Aesthetic Plastic Surgery, said he was surprised that the agency had estimated that silicone implants failed so often.
"That's certainly news and does need to be addressed," said Dr. Jewell, who has consulted for Inamed and Mentor. "But I feel that the devices should be approved."
The companies can track the safety of the devices after they are approved, he said. Women often find that silicone implants feel more natural than saline, Dr. Jewell said.
By GARDINER HARRIS