Silicone gel-filled breast implants have been on the market in the USA since 1963. In 1976, the Medical Device Amendments were enacted giving the FDA regulatory authority over medical devices, including silicone gel-filled breast implants . At that time, FDA planned to review medical devices based on their regulatory class (see Chapter 2), with a strategy of first reviewing devices with new technology or devices for which there was insufficient information to assure safety and efficacy. Based on the recommendation of the General and Plastic Surgery Devices Advisory Panel in 1978, breast implants were classified as class II devices: those for which general controls alone are insufficient to provide reasonable assurance of safety and effectiveness, but for which there is sufficient information to establish special controls. Advisory committees (panels) are groups of experts commissioned by the FDA to provide advice on questions posed by the agency .
In 1988, FDA reclassified all breast implants (silicone gel-filled and saline-filled - see below) into class III: devices for which there may be insufficient information to determine that the application of general controls alone, or general and special controls, are sufficient to provide reasonable assurance of safety and effectiveness (see Chapter 2). After this reclassification, in 1989 FDA announced its intention to require breast implant manufacturers to provide a premarket application (PMA) and produce studies to support the safety and effectiveness of breast implants. As required by law, FDA gave the manufacturers a minimum of 36 months to comply.
In the meantime, concerns were raised about the safety of breast implants. In 1989 an unpublished study showed that polyurethane foam, which was used as a coating on some silicone gel-filled breast implants to reduce capsular contracture, would degrade and release 2-toluene diamine (TDA), a chemical known to cause cancer in animals, under conditions of high temperature and alkalinity. The manufacturer removed these from the market in 1991. Based on a study by one of the manufacturers, FDA estimated that the risk of cancer from exposure to TDA is about one in 1 million over a woman's lifetime [4,5].
By the early 1990s there was growing concern about breast implants because of the potential for implants to break or leak silicone gel or shed silicone particles from the implant shell . It was not known how often implants ruptured or how often gel or silicone particles migrated out of the implant shell into breast tissue or beyond, neither was it known whether there were health consequences to implant rupture. There were also concerns about increased risk for connective tissue disease and cancer in women with implants.
Breast implant manufacturers sent information to the FDA to fulfill the requirement for premarket approval. In August 1991, the FDA determined that the information breast implant manufacturers had sent was inadequate to warrant a review. However, the issue had become controversial, and FDA sought outside advice from advisory committees (panels). Therefore, the FDA convened the General and Plastic Surgery Devices Panel in November, 1991, to consider whether there was adequate information on silicone gel-filled breast implants to permit continued marketing. Despite the Panel's opinion (which concurred with that of the FDA) that there was inadequate information to approve these devices, the Panel voted to keep silicone gel-filled breast implants on the market while manufacturers collected additional information to support the continued marketing of their product . Several months later, in early 1992, the FDA called for a voluntary moratorium (not a ban, as sometimes characterized) on the sale and implantation of silicone gel-filled breast implants until the Panel could meet again to consider additional information. This moratorium did not affect saline-filled breast implants. The additional information FDA wanted the Panel to consider included evidence that breast implants leaked or ruptured at an unknown rate, and some studies which had been published in the 1970s and early 1980s on a possible link between breast implants and connective tissue disease, which had not been included in the manufacturers' earlier submissions to the FDA. There was also growing concern that breast implants might cause an atypical connective tissue disease characterized by muscle and joint pain and fatigue. In addition, there was evidence that the manufacturing process to make breast implants was poorly controlled. The Panel reconvened in February 1992 and in March 1992 the FDA announced its decision.
FDA lifted the voluntary moratorium on silicone gel-filled breast implants and announced its decision to allow access to silicone gel-filled breast implants only in controlled clinical studies for reconstruction after mastectomy, correction of congenital deformities, or replacement of ruptured silicone gel-filled implants. Until these clinical studies (called adjunct studies) could be submitted by manufacturers and reviewed by FDA, the Agency authorized temporary limited distribution of silicone gel-filled implants for patients undergoing reconstruction on an urgent need basis, with an informed consent, based on the finding that there was a 'public health need' for implants for reconstruction but not for augmentation purposes. While this made silicone gel-filled breast implants unavailable for cosmetic breast augmentation, the FDA allowed that the companies could later conduct clinical trials that would include a limited number of augmentation patients (core studies) as well as reconstruction and revision patients.
Some physicians' professional societies questioned the FDA decision [7,8] and the FDA Commissioner defended the Agency's decision [9,10]. At that time, there were no epidemiologic studies to either refute or confirm that women with breast implants were at greater risk for debilitating connective tissue disease than women without breast implants, despite the fact that these devices had been marketed for nearly 30 years. In addition, in 1992, while it was known that silicone gel-filled breast implants ruptured and leaked, there was little information on how often this occurred or its consequences. In fact, there was not even the most basic descriptive epidemiologic information on the prevalence of breast implants in the US population, or firm estimates of the proportion used for reconstruction after cancer or for other medical purposes compared to implantation for breast enlargement (augmentation) in healthy women for cosmetic reasons.
Subsequent studies indicated that 0.5-2-million US women had breast implants and estimates indicated that the majority (60-80%) were for cosmetic augmentation, not reconstruction after breast cancer or trauma [11-13].
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