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FDA Panel will Scrutinize Non-MRI Breast Implant Rupture Rates
Apr 7, 2005, 15:11, Reviewed by: Dr.
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FDA points out that Inamed�s model uses the following assumptions: �that the silent rupture rate in the non-MRI cohort can be predicted from the MRI cohort; that averaging the increase in rupture rate at yearly intervals is appropriate; that the rate at which rupture occurs over time is constant�; and that averaging the augmentation, reconstruction and revision rupture rates is appropriate.
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By FDA advisory committe ,
FDA will solicit feedback from its General & Plastic Surgery Devices Panel on whether Inamed and Mentor�s non-MRI breast implant cohort groups accurately reflect true rupture rates.
The advisory panel will convene April 11-13 to review both firms� PMAs for silicone-filled breast implants.
Since the majority of ruptures for silicone breast implants are silent � and therefore unlikely to be detect�ed without magnetic resonance imaging � FDA�s draft questions ask whether the two companies �adequately characterized the rupture rate.�
Results from the firms� respective studies showed disparate reported rates between the MRI and non-MRI groups.
Approximately one-third of the 1,000 patients enrolled in Mentor�s pivotal study underwent serial MRI at one and two years following implantation. Rupture rates through three years were 0.5% for augmentation, 0.8% for reconstruction and 4.8% for revision, according to FDA�s draft panel questions for Mentor. However, no ruptures were reported in the non-MRI cohort.
To address FDA�s concerns with rupture rates over the anticipated device lifetime, Mentor used a case series of augmentation patients with subglandular implants who did not have capsular contracture or any recurrent surgical procedures, and who received a single MRI to screen for ruptures.
An estimated one-third of the 940 patients in Inamed�s core study also received a serial MRI at one and three years following implantation. Total rupture rates at four years were 3.4% for augmentation, 20.5% for reconstruction and 10.9% for revision, according to FDA�s draft panel questions for Inamed.
In Inamed�s non-MRI cohort, total rupture rates through four years were 1.1% for augmentation, 4.9% for reconstruction and 1.7% for revision.
Inamed modeled a hypothetical curve extrapolating the rupture rate seen in the core study to estimate a 14% by-implant, 10-year rupture rate for the augmentation, reconstruction and revision groups.
FDA points out that Inamed�s model uses the following assumptions: �that the silent rupture rate in the non-MRI cohort can be predicted from the MRI cohort; that averaging the increase in rupture rate at yearly intervals is appropriate; that the rate at which rupture occurs over time is constant�; and that averaging the augmentation, reconstruction and revision rupture rates is appropriate.
�There are other models which could be selected, which lead to higher rates of rupture,� FDA states. In a presentation summary, the agency considers that ruptures could increase linearly with time, or on a quadratic basis.
When Inamed went before the panel in October 2003, panelists similarly expressed concerns with silent rupture. Although the panel issued a positive recommendation for approval, FDA ultimately opted against approving the silicone implants.
In addition to rupture concerns, FDA�s draft questions address Mentor and Inamed�s proposed postmarket study plans. The firms both propose to provide physician follow-up for patients in their core studies, with MRIs occurring every two years through the 10-year mark.
Mentor plans to terminate follow-up for patients whose implants are removed during the 10-year period and who do not receive a replacement from the study, while Inamed will continue to follow them via telephone. Neither firm plans to collect data on children of women who have implants.
While safety and efficacy data will continue to be collected, Inamed does not intend to complete the quality-of-life questionnaire at the six, eight and 10-year marks.
In addition, Mentor plans to use three existing breast implant registries, involving �physicians who voluntarily collect local complication data when patients return for a visit.�
Although Inamed proposes to tap the Danish Registry or third-party organizations such as the National Institutes of Health to collect data addressing outstanding concerns with the 2003 panel review, the firm �did not describe any specific plans for using these sources of information,� FDA said.
Inamed also plans to link its voluntary registry, which gathers baseline and demographic data but no postoperative information, to its rupture warranty program.
Although FDA�s questions regarding Inamed and Mentor�s applications are similar, the agency is soliciting feedback on whether Mentor�s implants are efficacious. Inamed successfully demonstrated efficacy at its 2003 panel review. 
- General & Plastic Surgery Devices Panel
FDA advisory committe
This meeting will be held April 11, 2005 at the Hilton, Gaithersburg, Md. beginning at 8 a.m.
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