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Breast Implants, Breast Cancer, and Cancer Detection Introduction Safety testing to determine whether silicones cause cancer in laboratory animals has been conducted for many years. Those tests, which are part of more than thirty years of research and over 3,000 studies on the safety of silicones, continue to show no connection between silicone in medical applications and cancer in humans. The first allegations on the potential health effects of breast implants were made following case reports and animal studies, when it was suggested that women with silicone breast implants would have an increased occurrence of breast cancer. In addition, it was suggested that, because the implants were largely radiopaque, their presence might significantly delay cancer detection and thereby negatively impact the prognosis of women with breast implants who did develop the disease. The assumption was that breast cancer among women with implants would be in a more advanced stage of disease when first detected and, consequently, survival among these women would be diminished. However, with remarkable consistency, the controlled human health studies indicate that the incidence of breast cancer is not increased and the detection of this malignancy is not delayed among women with silicone breast implants. In fact, both the human health studies and experimental animal studies suggest silicone breast implants may be associated with a decreased risk for breast cancer.1-16 Breast Cancer Incidence According to the American Cancer Society (ACS), over a lifetime, one in eight women will develop breast cancer. Several risk factors have been identified including: age, race, gender, genetics, age of mother at birth of her first child and hormone replacement therapy. Breast cancer increases markedly with age, especially among those over 50. It is more common among Caucasian than African-Americans. It is primarily (although not exclusively) a disease of women.17 About 5% of women with breast cancer have a hereditary form. Late child-bearing (over the age of 30) puts women at increased risk. And there is some evidence of a slight increased risk among those with 10 or more years of hormone replacement therapy.18 All the epidemiology studies have found that breast cancer occurs with the same or possibly less frequency among women with breast implants than among women who do not have these medical devices. These studies were conducted in the United States (U.S.), Canada, Sweden, Denmark and France and the conclusion of no association between breast implants and breast cancer has been notably consistent. In Los Angeles, a study of 3,111 women found 9 cases of breast cancer among women with breast implants whereas 15.7 were expected.7 While this finding was not statistically significant, subsequent work _base_d on additional years of follow-up of these women achieved comparable results which were statistically significant.5 Results obtained from a population-_base_d study by the U.S. National Cancer Institute (NCI) of 2,174 breast cancer cases and 2,009 controls reached a similar conclusion.3 Comparable findings have come from Canada. _base_d on data for 11,676 women who underwent cosmetic breast augmentation in the Canadian province of Alberta, Berkel and associates reported more than a 50% deficit of breast cancer among the breast implant group compared to the general population.1 In other words, the Berkel research not only refuted the original hypothesis, it reported statistically significant results that appeared to be more consistent with exactly the opposite conclusion: breast implants were somehow protective against cancer. At the time, many were skeptical of this research because it appeared so counter-intuitive. Although later reanalysis of this work did not find as dramatic a reduction in breast cancer among women with implants, Bryant and Brasher confirmed there was no added risk due to breast implants.4 Researchers at the University of Toronto reported preliminary results for a government-funded study of about 7,600 implanted women and 4,000 controls.19 Again, women with breast implants had a lower occurrence of breast cancer. Similar findings have come from Europe. In a study from France, women reconstructed with silicone breast implants following breast cancer surgery had a lower mortality rate as compared with women who did not have reconstruction.16 A study of 1,135 Danish women with cosmetic implants, found no difference in occurrence of breast cancer among women with breast implants compared to women without breast implants.8 Investigators in Sweden identified women who had received breast implants for non-medical (cosmetic) reasons.13 With an average duration since implant of 11.7 years, they observed 7 breast cancers whereas 11.2 were expected. Subsequently, with a longer period of follow-up, they observed 18 cases with 25 expected.12 Although the mechanisms underlying the possible decreased risk are not known, similar results have been demonstrated in laboratory animals. Su, et al., studied the effect of silicone implants in rats and mice. Among mice known for spontaneous formation of mammary tumors, the placement of a silicone implant in the mammary region decreased the occurrence of mammary tumors. A similar, statistically significant, effect was found among rats that received mammary implants.20 In summary, women with breast implants are not at higher risk for breast cancer. For reasons yet to be determined, they actually appear to have a lesser risk for the dreaded disease. Sarcoma Sarcomas or solid state tumorigenesis, also referred to as the Oppenheimer effect, has little significance for humans.21 This phenomenon occurs in rodents, and it is a phenomenon common to many materials. By way of background, sarcomas occur in rodents at a fairly high frequency at the site of implantation, up to 30% or 40%, when materials of a sufficient size and shape are implanted. This happens in rodents irrespective of the chemical composition of the implanted material. It has been observed with glass, gold, stainless steel, other _meta_ls used in medical devices, and various types of non-silicone polymers.22 Over ten years ago, the Commissioner of the Food and Drug Administration (FDA), concluded-with respect to silicone breast implants-that these types of tumors are unlikely to occur in humans and that insufficient evidence exists to establish an 'unreasonable and substantial risk' that could be attributed to the device. 23 Two in-depth reviews on this matter were sponsored by FDA; one was an interagency effort by FDA and the National Institutes of Health (NIH), the other was conducted by an FDA Cancer Assessment Committee. An NIH-sponsored review of the issue of breast implants and cancer stated, ?two expert committees commissioned by the FDA to review this issue concluded that the tumors were due to nonspecific solid-state carcinogenesis and that this phenomenon in rodents did not appear to be relevant in humans. 24 While sarcomas may appear in humans, irrespective of the presence of any type of implanted material, they are rare. Relative to breast implants, if their use resulted in the increased development of breast sarcomas, one would expect to see an increase in the occurrence of these tumors in conjunction with the increase in the use of breast implants over time. A study conducted in the U.S. and _base_d on the Surveillance, Epidemiology and End Results (SEER) data, May and Stroup25 noted that the incidence rates for fibrosarcoma and other soft-tissue sarcomas of the breast among women were very low and did not increase over time. Furthermore, no sarcomas of the breast were observed in various analytic epidemiology studies on breast implants conducted in Sweden,12 Great Britain,15 Denmark,8 Canada,2 or the U.S.5 Morgan and Elcock analyzed data from a case-control study _base_d on military medical records. They found no statistically significant association between soft tissue sarcomas and various types of orthopedic materials or other _meta_l or plastic implants.26 That is comforting in view of the large number of people with various types of pins, plates, staples, screws, sutures, shrapnel, shunts, tubes, pacemaker leads and other medical devices in their bodies. In summary, although solid state tumorigenesis is an interesting phenomenon that occurs in rodents, medical implants-including silicone breast implants-are not related to an increased risk for sarcomas in humans. Mammography among Women Without Breast Implants A variety of procedures have proved effective in the early detection of breast cancer, the two most commonly used being breast self-exam (BSE) and mammography, alone or in combination. Mammography is felt to offer the opportunity of detecting a malignancy during that period when it might not be easily palpated;27 but it is not a perfect tool. There will be false positive findings (i.e., a number of women who have routine periodic mammographic examinations will be provisionally diagnosed with breast cancer and later found to be healthy) and false negative findings (i.e., women will be told that their mammogram is normal but within one year breast cancer will be detected).28,29 For example, in a study sponsored by the ACS and the NCI, 280,000 women underwent history, physical examination, and mammography. Mammography alone detected only 42% of the cancers.30 Another study reported a 10%-15% false-negative rate, that is, 10%-15% of women who were told their mammograms were normal actually had breast cancer.27 An NCI website points out that screening mammograms miss up to 25% of breast cancers in women in their forties compared to about 10% among older women.31 Depending on the number of screening procedures used (either mammography alone, clinical breast examination alone or both procedures) as well as the number of images taken, Baines and Miller found that the sensitivity of mammography ranged from 53% to 81% among women 40-49 years of age.32 Several factors contribute to the quality of mammographic imaging, irrespective of the presence of breast implants including: dedicated equipment that is designed specifically for mammography;28,33 technicians who are specially trained in proper patient positioning and breast compression; proper film processing; and radiologist who are experienced in interpreting mammographic exams.27 With respect to mammography in the presence of breast implants, special procedures to aid in viewing as much breast tissue as possible and four or five views of the breast are recommended.34,35 Do Breast Implants Delay Detection of Breast Cancer? Some clinicians have suggested that silicone breast implants interfere with mammography and thereby delay the detection of breast cancer.36-41 Data from well-defined populations do not support this hypothesis. There are two possible reasons why delayed detection does not appear to be a problem. One, if a radiologist is aware of the presence of breast implants, modified mammographic techniques are used to provide better views of the implanted breast.34,42,43 And two, some have suggested that palpation of the breast may be aided by the presence of a breast implant.33,44 Irrespective of whether a woman does or does not have breast implants, it is important that she participate in a routine program of breast cancer detection, one that includes breast self-exam and mammography.34,35 Or as one researcher stated, good patient follow-up and careful mammography appear to obviate [prevent] the problem45 of delayed detection. Amidst reported concerns about delayed detection and more advanced stage of disease at time of diagnosis, Brody and Deapen reported finding no difference between women with breast cancer and implants compared to women with breast cancer without implants at time of diagnosis.46 After additional follow-up of their study population, the researchers stated, We found no difference in breast cancer stage at diagnosis among implanted women as compared with the general population. 5 Researchers at the University of Calgary Foothills Hospital studied the stage at detection and survival experience of 41 women who developed cancer after cosmetic breast implantation compared with all other women diagnosed with breast cancer in Alberta from 1973 to 1990. The tumors in women with breast implants were smaller when detected as compared with the tumors in women without implants, but lymph node and distant _meta_stases were equally frequent in the two groups. The researchers concluded, ?women with breast implants in whom breast cancer develops are not diagnosed in a later stage and do not experience an impaired survival as compared with breast cancer patients without implants. 2 The finding that breast cancer is not detected at a later stage and survival is not compromised among women with breast implants is supported by the work of others.3,8,16,47-50 After an extensive literature review on the safety of breast implants, the Institute of Medicine concluded, These data present a consistent picture that implants do not increase breast cancer recurrence rates or decrease survival rates in patients after reconstruction with implants. 51 A similar conclusion was reached by Health Canada which states, There is no scientific evidence that women with saline-filled, silicone gel-filled or polyurethane foam covered silicone gel breast implants are more susceptible to cancer than other women. Also, there is no evidence that cancer, if it develops, is detected later in patients with implants. 52 Other independent groups have reviewed the breast cancer-breast implant literature and have concluded that women with breast implants do not get breast cancer more frequently than women without implants.53-55 In summary, breast cancer detection is not delayed in women with breast implants. Furthermore, when women with breast implants do get breast cancer, they do not suffer a poorer prognosis. Prepared by Dow Corning Corporation 22 November 1999
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