Still, several panelists said they were uneasy with how the patients and physicians would use the implants because of the extreme difficulty in detecting ruptures in the two companies' studies. More than 85% of ruptures in Inamed's study occurred with no symptoms, while all of the ruptures in Mentor's trial had no outward signs and required imaging of the breast (an MRI scan) to detect them.
That fact led several experts to worry that thousands of women could go for years with broken implants in their bodies while there are still some questions about the health effects of leaked silicone.
Thousands of women have blamed ruptured implants for diseases including autoimmune disorders and cancer, though a 1999 Institute of Medicine study found no hard link between the products and systemic disease. Still, that same year, former implant maker Dow Corning agreed to pay $3.2 billion to settle health claims in a major class-action lawsuit.
The problem of "silent" implant rupture led experts to predicate their approval on a recommendation that women undergo an MRI scan five years after receiving their implants and that the devices be removed if breaks are found.
The panel also recommended that all patients be required to receive education and sign an informed consent form before surgery. The panel also recommended that only physicians who undergo a certification course be allowed to use them in surgery.
"The access needs to be limited. Don't just assume physicians have had this training," said Michael J. Miller, MD, a panel member and plastic surgeon from the University of Texas.
Panelists took the unusual step of requesting that silicone implants be closely tracked to allow the company and regulators to follow each device to individual patients in the event of future problems. The committee also said that the company must continue its study of breakage rates for seven more years.
"I think that it's still too soon to accurately define what is happening to that group," said Patricia Newburg, MD, a panel member and dermatologist from Scarsdale, N.Y. Newburg pointed to data that showed that women with ruptured implants were more likely to experience joint pain consistent with connective tissue disease, though the small study had too few participants to be significant.
"In short, there's too much uncertainty," said Newburg, who voted against both companies' implants.
Levine told the panel that the Mentor's "postmarket commitments would be followed."
Tough Choices for FDA
This week's split vote is likely to put FDA officials in a difficult position when deciding if, and how, to approve silicone implants, said Diana Zuckerman, president of the National Research Center for Women and Families, a group that opposes their approval.
The FDA withheld approval of Inamed's implants despite an advisory panel's recommendation 18 months ago, citing incomplete safety data. As on Wednesday, the panel at that time insisted on a set of strict approval conditions agency officials did not attempt to enforce.
"I think there will be a lot of pressure to take the same action on both" Inamed and Mentor implants, Zuckerman told WebMD. "It shows a level of concern that's not consistent with approval."