Silicone gel implants were highly popular until the Food and Drug Administration ended routine sales in 1992, restricting them to breast cancer patients in strictly controlled clinical trials because of concern that leaking silicone could cause serious illnesses.
Now Inamed Corp. wants to restart sales with new, improved silicone implants, arguing the implants have been exonerated.
Indeed, studies to date show little evidence the implants cause major diseases like cancer or lupus.
But the FDA worries that rare diseases aren't settled, and that subsets of women — especially the small proportion who have silicone leaking through scar tissue into the breast or beyond — might be more vulnerable to painful conditions like fibromyalgia.
These silicone implants also are said to be softer, more natural feeling than widely available saline implants, reports CBS News Correspondent Elizabeth Kaledin.
The agency convened a two-day meeting for its scientific advisers to analyze all the evidence. They are scheduled to make recommendations on Inamed's fate Wednesday. The FDA won't be bound by the panel's advice, but usually follows it.
After 16 hours of testimony and debate Tuesday, the advisers cited a big problem: Research by FDA and others suggest implants really start breaking and leaking seven years after women receive them, but Inamed hasn't tracked women's health for nearly that long.
"A decade has passed and we sat here today talking about two- and three-year data. I'm flabbergasted," said Dr. Thomas Whalen of the Robert Wood Johnson Medical School, the advisory panel's chairman.
"It simply boggles the mind," agreed fellow panelist Nancy Dubler, a bioethicist at Albert Einstein College of Medicine — who also asked why Inamed hadn't solved the problem by making implants more durable in the last decade.
"The FDA and the company don't seem to have been willing to wait long enough to get enough information to make a really good judgment about the safety of these implants," Public Citizen's Dr. Sidney Wolf told CBS News.
But even after three years, up to 46 percent of silicone implant recipients in a key Inamed study needed additional surgeries because of painful scar tissue and other complications. Up to a quarter of the women had to have the devices removed or replaced.
And in some women — about 6 percent of breast cancer survivors, fewer women who get the implants for enlargement — the implants silently break, leaking without immediate symptoms to signal that they should be removed.
"What is happening to that silicone?" asked FDA adviser Barbara Manno, a toxicologist at Louisiana State University.
Silicone implants break no more often and require no more extra surgery than do implants filled with salt water that currently are Americans' main option, argued Inamed executive JoAnn Kuhne.
"We really stand behind our data and we feel that the science really prevails and shows that these breast implants are perfectly safe and effective," Kuhne told CBS News.
Inamed will answer some of the outstanding questions by continuing to track the health of patients in its key study for another seven years, even if the implants are allowed to sell in the meantime, she pledged.
And a string of women implored the FDA to allow them to make the choice, arguing that silicone implants are more natural feeling than saline implants, which aren't perfect either.
"If the implants are approved for general use for all purposes, then I think there will be a huge increase in demand because the implants feel better," said Dr. Nolan Karp, a plastic surgeon.
But dozens of other women told FDA that implants left them with disabling pain and disfigurement — problems that often struck once they'd had the implants for a decade or more.
"I've got the chronic fatigue, I've had sleep disorders, I have night sweats, it goes on and on and on," said Pam Noonan Saraceni, adding that the average woman doesn't understand the risks.
"She needs to know about the local complications. She needs to know that they rupture," Saraceni told CBS News.
The advisers were moved by that testimony, repeatedly questioning why Inamed hadn't tracked women long enough to prove just how big a problem those complaints are.
But in debate that stretched past midnight, they were torn on how to settle the concerns — or if women should be able to choose silicone implants knowing there are still unanswered questions.
"I believe in the right to choose," said FDA panelist Dr. Benjamin Anderson, a University of Washington cancer surgeon. But he stressed if that's ultimately the decision, women will need some basic guidelines on how often to check for leaks and when to remove old implants — information also still up for debate.