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Large Study Finds No Link Between Silicone Breast Implants and Breast Cancer Risk (dateline October 6, 2000)

A large study conducted by researchers from the National Cancer Institute (NCI) finds no correlation between silicone-filled breast implants and breast cancer risk. Silicone implants had been on the market since 1962 but were banned by the U.S. Food and Drug Administration (FDA) in 1992 after questions arose concerning the safety of silicone leakage in the breast tissue and other areas of the body. The NCI study, revealing no increased breast cancer risk from silicone implants, is the first part of an analysis ordered by the U.S. Congress to evaluate the long-term health effects of silicone implants.

In the study, researchers analyzed medical records and collected data from 13,500 women who had implant surgery for cosmetic reasons between 1962 and 1989. These women were compared to both the general population and to women who had received other types of plastic surgery. The average length of follow-up was 12.9 years among the women with implants and 11.6 years among the comparison group.

"For women followed for more than 10 years, there was no change in breast cancer risk," said Louise A. Brinton, PhD, principal investigator from the NCI’s Division of Cancer Epidemiology and Genetics (DCEG) in Bethesda, Maryland, in a press release. The NCI study is one of the largest studies on the long-term health effects of silicone breast implants ever conducted. However, the study only included women who had implants placed for cosmetic reasons and did not include any breast cancer survivors.

According to the NCI, breast implants have also been linked to later breast cancer diagnoses. This may be due to the fact that the x-rays used for mammographic imaging of the breasts cannot penetrate silicone or saline implants well enough to image the overlying or underlying breast tissue. This makes cancer more difficult to detect at an earlier age. Therefore, some breast tissue (approximately 25%) will not be seen on the mammogram, as it will be covered up by the implant. In order to visualize as much breast tissue as possible, women with implants typically undergo diagnostic mammography instead of screening mammography. Diagnostic mammography requires additional mammography views.

In the NCI study, the researchers did find that breast cancer was detected at a later stage among some women with breast implants, compared to women without implants. Also, fewer cases of early stage " in situ" breast cancer (cancer that has not spread past the boundaries of tissue where it originally developed) were also found among women with implants, compared to women without implants. However, the researchers say that the differences were not statistically significant and require further investigation.

According to the NCI, it is estimated that between 1.5 million and 2 million American women have had breast implant surgery since implants first appeared on the market in 1962. Approximately 80% of women get breast implants for cosmetic reasons and 20% get implants to reconstruct their breasts after breast cancer surgery (mastectomy). Before silicone breast implants were banned, over 90% of implants contained silicone, since these implants were thought to cause the enhanced breast to look and feel more natural than saline (salt water) filled implants. Currently, only breast cancer patients who participate in closely monitored clinical trials may get silicone breast implants.

There is much controversy surrounding silicone breast implants. Many medical experts doubt silicone implants cause any significant medical disease. However, many women who experienced silicone leakage have reported symptoms such as breast pain, fatigue, myalgias (muscle pain), arthralgias (joint pain), hair loss, and memory loss. Future research will help to better understand the long-term health effects of silicone breast implants.

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