TUESDAY, April 12 (HealthDay News) -- Silicone gel breast implants still haven't been proven safe, so the devices should not be allowed back on the American market, a U.S. Food and Drug Administration advisory panel decided Tuesday.

The 5-4 vote to reject Inamed Corp.'s request to start marketing a new version of the implants after a 13-year ban followed two days of hearings in Washington, D.C.

On Tuesday, before the vote, Inamed officials testified that today's implants are less prone to rupture and leakage than the devices that were all but banned in 1992 because of potential health concerns.

But the FDA scientific advisors appeared skeptical, saying significant questions still persisted on how long the implants last inside a woman's body -- and the health consequences when they break, the Associated Press reported.

Most on the panel members said they felt the implants were "reasonably safe" in the first three years of use, the AP reported. But they were split on long-term durability, and many worried that one implant model targeted to breast cancer patients actually is the most prone to breaking.

In its testimony earlier Tuesday, Inamed said its studies led it to conclude that about 14 percent of implants will break within 10 years, a figure far lower than the 93 percent estimate provided by health regulators before the hearings.

But FDA statistician Pablo Bonangelino told the panel, "In fact, we really don't know" how many implants will last even 10 years.

Despite the vote, taken at the end of the day, the panel on Wednesday is scheduled to consider an application by Inamed competitor Mentor Corp. to market its own silicone implants.

Both companies contend that thicker shells and stickier silicone make newer implants safer -- and that U.S. women deserve the option to choose. Silicone implants look and feel more natural than the salt water-filled implants on the U.S. market, and they are far preferred in Europe where both types are sold, the companies said, according to AP.

On Monday, as the hearings opened, the panel listened to emotional testimony mainly from women who have used silicone implants.

Some women detailed what they called devastating health problems caused by the devices. Other women, however, called the silicone implants a superior product to saline implants for breast enhancement or breast reconstruction following cancer surgery. They also said consumers should be allowed to chose freely between the two.

The hearings are the latest in the long and contentious history of silicone implants.

Silicone gel implants went on sale in 1962, before the FDA monitored safety issues closely. Thirty years later, the agency banned all but those used for breast cancer reconstruction, amid fears that leaks might be responsible for autoimmune diseases and even cancer. Other problems included the fact that many women needed repeat operations to deal with painful scar tissue.

By 1998, more than 170,000 lawsuits had been filed against implant manufacturers by women claiming their silicone implants had caused immune system disorders and chronic diseases such as rheumatoid arthritis and systemic lupus. Four companies paid out millions of dollars in settlements to the women, and one of them, Dow Corning, filed for bankruptcy to pay $3.2 billion to settle its claims.

Studies by the Mayo Clinic, Harvard Medical School and the Institute of Medicine (IOM) panel from the National Academy of Sciences subsequently found no evidence that leaked silicone from gel implants caused systemic disease.

More recent research, however, has focused on the problems of scar tissue developing at the site of the implant and on the rate of rupture of the devices.

The rupture rate was a prime reason that FDA refused last January to allow the devices back on the market.

In doing so, the agency overruled another panel of scientific advisors who voted 9-6 in October 2003 to let the devices back on the market with a series of strict conditions that included warnings to users and more safety tests.

Panel chairman Dr. Thomas Whalen publicly disagreed with the decision and sent a letter to then-FDA Commissioner Mark McClellan and five members of Congress citing his "strong reservations" about the vote and "imploring" them not to approve the product.

In rejecting the advisory panel's recommendation last year, FDA officials made it clear, however, that the agency was not closing the door.

"This is still an application that is under review," said Dr. David Feigal, director of the FDA's Center for Devices and Radiological Health.

At the same time, the agency laid out a new guidance document for all makers of breast implants that included new recommendations for mechanical testing, modes and causes of rupture, clinical study information, post-approval requirements and labeling.

More information

The FDA has more on breast implants.