The staff of the Food and Drug Administration on Wednesday criticized data provided by two companies seeking approval for cosmetic surgery use of silicone-gel breast implants.

The FDA staff, which analyzed such issues as implant rupture rates and health consequences of ruptures, said the companies provided insufficient information about the long-term effects of these products.

The words "limited value" frequently appear in FDA staff comments about data in applications from

Inamed

(IMDC)

and

Mentor

(MNT)

.

In midafternoon trading, shares of Mentor declined 64 cents, or 2%, to $32.12, and shares of Inamed lost 98 cents, or 1.4%, to $67.12.

Silicone-gel implants haven't been allowed for cosmetic surgery in the U.S. since 1992, when the FDA imposed more stringent health and safety test requirements than had been previously mandated. The first U.S. silicone-gel implant was sold in 1962; Congress provided the FDA with regulatory authority in 1976.

Silicone-gel implants are still allowed in the U.S.

for a small number of procedures, such as breast reconstruction after mastectomies. But the big market for these devices is cosmetic surgery. FDA-approved saline, or salt-water-filled, implants are available for cosmetic surgery but are considered to have a less natural look and feel.

The FDA staff reports, published on the FDA Web site, were issued in advance of three days of agency advisory panel meetings starting on April 11. Staff reports are routinely issued before such meetings, and the staff offers a series of questions for these outside advisors. The agency doesn't always follow the recommendations of its advisers, but it usually does.

Commenting on Inamed's application, which included one study containing three full years of data, and partial data for a fourth year, the FDA staff report says, "it is difficult to reasonably predict the probability of rupture through year 10 with the available data."

The report adds that "the data are of limited value to address the local health consequences" -- problems at the rupture site -- because the Inamed study contained too few patients and because some patients hadn't received follow-up evaluations.

Another Inamed study was criticized for having a low follow-up rate for checking ruptures and for the lack of screening for certain implant ruptures. This study "is of limited value" in assessing rupture rates and the health consequences over time, the FDA staff says.

A study from Denmark, used in Inamed's application, was criticized by the staff because it contained information from several implant manufacturers, but it didn't cover Inamed's implant.

This is Inamed's second recent attempt to secure FDA approval for a silicone-gel implant. In October 2003, an FDA advisory committee voted 9-6 to approve the implant. But in January 2004, the FDA rejected Inamed's implant, saying the company's data "did not provide a reasonable assurance of safety of the device."

Mentor's application didn't fare much better. The company provided rupture rate data for two full years and partial data for a third year, which means the company did not assess the prospects of implant ruptures over the lifetime of the device, the FDA staff says.

The FDA staff report also says the data "are of limited value" to evaluate health consequences at the rupture site.

Mentor used the same Danish implant study that Inamed had cited, and the FDA staff issued the same criticism because the study didn't include Mentor's implant.

Mentor also provided other research studies on the health consequences of silicone-gel implant ruptures, but the FDA staff says the research doesn't answer all of the FDA's questions about health issues and the research doesn't focus on Mentor's implants.

The FDA staff asked the advisory panel to pay close attention to both Mentor's and Inamed's applications for so-called silent ruptures of implants. Because silicone gel is thick, women run the risk of not being aware their implants have ruptured. "You should consider that most ruptures are silent, and that there is difficulty in ensuring routine MRI examination for women with breast implants," the FDA staff tells advisory panel members.

The staff asks the committee members to decide whether both companies have "adequately characterized the rupture rate and how this rate changes over the expected lifetime" of their devices.