In one of the largest studies on the long-term health effects of silicone breast implants, researchers from the National Cancer Institute found no association between breast implants and the subsequent risk of breast cancer. The study will be published in the November issue of Cancer Causes and Control.
Breast implants first appeared on the market in 1962. Manufacturers initially assumed that the implants were biologically inactive and, therefore, would have no harmful effects. However, over the past 2 decades there have been a number of reports of connective tissue disorders and cancers among implant patients.
In 1992, because of the lack of sufficient evidence on the long-term safety of implants, the U.S. Food and Drug Administration restricted the use of silicone breast implants to women seeking breast reconstruction in controlled clinical trials, and Congress directed the National Institutes of Health to undertake a large follow-up study to evaluate the long-term health effects of the implants.
"This is the first part of our analysis of the health risks from the study," said Louise A. Brinton, Ph.D., principal investigator from NCIs Division of Cancer Epidemiology and Genetics. "For women followed for more than 10 years, there was no change in breast cancer risk. Our results do not confirm the findings from several other studies that exposure to implants reduces a womans risk for breast cancer. This may relate to the longer follow-up in this study as compared with most others."
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"This study is an important and welcomed addition to the substantial body of prior work," said Stuart Bondurant, M.D., professor of medicine and dean emeritus of the School of Medicine at the University of North Carolina, Chapel Hill. "In science, every added piece of evidence is useful and important, and this is no exception." Bondurant was the chairman of the Institute of Medicine committee that released a report last year that found no link between breast implants and cancer, immunological diseases, neurological problems, or other systemic diseases (see News, July 21, 1999, p. 1191). The IOM report was released after the NCI study was under way.
The participants in the NCI study included 13,500 women who had implant surgery for cosmetic reasons in both breasts sometime between 1962 and 1989 and, for comparison, about 4,000 women similar in age who had some other type of plastic surgery, such as removal of fat from the stomach, or wrinkles from the face and neck. Both groups of women were selected from 18 plastic surgery practices in which the surgeons had performed large numbers of cosmetic breast implant surgeries prior to 1989 and were willing to give the investigators access to their records. The practices were located in six geographic areas: Atlanta; Birmingham, Ala.; Charlotte, N.C.; Miami and Orlando, Fla.; and Washington, D.C.
To carry out the study, researchers reviewed the medical records from the plastic surgery practices and collected data about the surgical procedures, types of implants, and complications, if any, as well as factors affecting health status, such as weight and medical history. Patients who were located were asked to complete a mailed questionnaire to collect information about their health status, factors that might affect their health, and short- and long-term complications that might be associated with the implants.
The breast implant patients were compared to both the general population and to women who had received other types of plastic surgery. In previous reports, the general population was used as the control group. However, an earlier study found that women with implants tend to share more breast cancer risk factors with women who had received other types of plastic surgery than with the general population. When compared with either the general population or women with other types of plastic surgery, there was no evidence of a change in breast cancer risk in the implant group.
Typically, implants are soft silicone sacs, inflated with either saline solution (salt water) or a synthetic silicone gel. Both have been marketed since 1962. Before the 1992 FDA ban, 90% to 95% of the implants contained silicone gel because they had a more pleasing look and feel than the saline-filled implants. Since 1992, 90% to 95% of the implants have been saline-filled. It is not known how many women have silicone versus saline implants.
Of the implant patients in the study, 49.7% received silicone gel implants, 34.1% double lumen implants, 12.2% saline-filled implants, 0.1% other types of implants, and 3.8% unspecified types of implants. (Double lumen implants have two shells; the inner sac is filled with silicone gel and the outer with saline.)
The participants had cosmetic surgery during a time (between 1962 and 1988) when a great number of changes were taking place in the manufacturing of breast implants such as the shell thickness, the type of shell coating, and the gel composition. However, the researchers found there was no altered breast cancer risk associated with any of the types of implants.
Bondurant emphasized that the primary health concern regarding breast implants is the high incidence of local complications, a conclusion the IOM committee reached last year. "Local complications are substantial and frequent," he said. "There was concern that attention to local complications had been diverted away by the unjustified attention to cancer and other diseases." He said he hoped the IOM report and the results of this latest study can help refocus efforts to study the incidence of such complications as disfigurement, pain, and discomfort.
About 80% of breast implants in the United States are for cosmetic reasons and 20% for breast reconstruction. This study does not include women undergoing breast reconstruction after breast cancer surgery, so it is not possible to predict whether similar results would be found for this population. The majority of the previous studies have also focused on women who received implants for cosmetic reasons.
It is estimated that between 1.5 million and 2 million U.S. women have had breast implants since they first appeared on the market in 1962. Future analyses of the data will evaluate the risk of other cancers, connective tissue disorders, and causes of death.
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