Introduction
In the late 1940s, a family of silicon-based polymers (plastics)
was developed. These polymers had a molecular structure of silicon
and oxygen atoms with various organic sidechains, which could be
varied to make the silicones liquid or solid for use as lubricants,
gels, flexible sheeting or solid blocks of low reactivity and great
permanency. Silicones were rapidly taken up by surgeons as a compatible
material for implanting into the human body.
Breast augmentation was first performed by injecting paraffin
wax into the breast and, in 1949, by the implantation of polyvinyl
alcohol sponge. As these implants set like a rock after several
years, injectable liquid silicone was tried in Asian countries
(it was never legal in Australia). However, this produced granulomas
with hard lumps and opacities which precluded mammographic detection
of breast cancer.
Silicone gel-filled prostheses were first used in 1964 and it
has been estimated that about two million have been implanted
over 30 years worldwide. The prostheses have been modified to
include fixation patches, thinner outer envelopes of silicone,
silicone cores with outer envelopes of saline, and textured outer
envelopes. Regulations governing the use of breast implants in
Australia are shown in Box 1.
Silicones are currently used not only in gel-filled breast implants,
but also in ventriculocaval shunts, artificial joints and tendon
sheaths, intraocular lenses, cochlear implants, as well as implantable
pumps, pacemakers and defibrillators.
Problems with silicone gel breast implants
Mechanical problems
The fibrous tissue "capsule" that naturally forms around
the implant can contract, increasing tension in the prosthesis
and causing pain, hardening and changes in breast appearance.
Sometimes "bleeding" of silicone gel into the space
between the envelope and the capsule occurs with an apparently
intact envelope.
External trauma can rupture the implant, causing leakage of silicone
gel into the capsule or migration of silicone to other body tissues.
The prosthesis may cause local infection.
A 1994 study reported that 10% of prostheses needed replacement
and, of these, 85% were intact and 15% had bled or had ruptured
(i.e., only 1.5% of all prostheses had bled or leaked and 98.5%
were intact). 2
Relationship to autoimmune diseases
During the 1980s, there were sporadic References in the
literature to single cases or small series of cases where an association
between silicone gel implants and autoimmune diseases was claimed.
3-6 The hypothesis that silicone induces connective-tissue diseases
was generated from such descriptive uncontrolled studies. 7 Up
to June 1993, about 300 patients have been reported worldwide
with rheumatic symptoms after receiving gel-filled breast implants.
8 The most commonly reported connective-tissue disease was scleroderma,
but several other connective-tissue disorders and vague musculoskeletal
symptoms have also been described, particularly vague aches and
pains (fibromyalgia), sleep disorders and fatigue -- symptoms
which are extraordinarily common in the community. 9
It was not until 1994 that the first definitive studies to examine
the relationship between silicone implants and autoimmune disease
appeared. Englert et al. identified 556 cases of scleroderma in
women who had resided in Sydney between 1974 and 1988, of whom
270 were living and 213 were deceased (73 were "living status
unknown"). 10 They reported that the rates of augmentation
mammoplasty were similar between the 251 women with scleroderma
that they interviewed and 289 matched controls (the study carried
a 90% chance of detecting a relative risk of 4.5). These results
were validated in 1996 when the authors found no association between
silicone breast implants and scleroderma (odds ratio [OR], 1.33;
95% confidence interval [CI], 0.26-6.71, and OR, 1.00; 95% CI,
0.16-6.16, after adjustment for confounders age, socioeconomic
status and ethnicity). 7 Validation of augmentation mammoplasty
status was possible in 532 of the original 556 cases of scleroderma.
Larger epidemiological studies were conducted in the United States.
In 1994, Gabriel et al., from the Mayo Clinic, performed a population-based
case-control study of 749 women who had received a breast implant
in Olmsted County, Minnesota, between 1964 and 1991. 11 Each subject
was matched with two women of the same age who had not had a breast
implant, but had had a medical evaluation within two years of
the date of the subject's implant. The implant group were followed
for a mean of 7.8 years and the control group for a mean of 8.3
years.
The authors sought evidence from the medical records for a diagnosis
of any connective-tissue diseases, autoimmune diseases or non-breast
cancer, as well as for related symptoms. Only morning stiffness
was significantly more common in the implant group. Five women
with implants and 10 women without implants were diagnosed with
one of the specified connective-tissue diseases. The authors found
no statistically significant elevation in the relative risk of
any of the specified connective-tissue diseases or other disorders
in women with silicone breast implants.
Box 2 shows the conclusion reached in 1994 by the Medical Devices
Agency of the United Kingdom Department of Health, which reviewed
all the evidence relating to silicone breast implants and connective-tissue
disease.
In 1995, Sanchez-Guerrero et al., from Harvard Medical School,
reported on a cohort of over 120 000 registered nurses aged between
30 and 55 who had been followed up since 1976. 13 The mean follow-up
period after surgery for the 1183 women with silicone breast implants
was 9.9 years.The age-adjusted relative risk of definite connective-tissue
disease in women with implants was 0.3 (95% CI, 0-1.9). The relative
risk of self-reported signs or symptoms of connective-tissue disease
for women with implants was 1.5 (95% CI, 0.9-2.4), and the risk
of having any one of 41 signs, symptoms or laboratory features
of connective-tissue disease was 0.7 (95% CI, 0.3-1.6). The authors
concluded that there was no association between silicone breast
implants and connective-tissue diseases, or signs or symptoms
of these diseases.
The American College of Rheumatology released a statement in
October 1995 declaring that these studies provided compelling
evidence that silicone implants expose patients to no demonstrable
additional risk for connective-tissue or rheumatic disease. 14
The College affirmed that anecdotal evidence, while of importance
in drawing attention to a potential problem, should no longer
be used to support this relationship in the courts or by the Food
and Drug Administration (FDA). They recognised that many women
who have received silicone breast implants have musculoskeletal
complaints that are also very common in the general population.
They had stated in 1994 the importance and great need for scientific
analysis of this question, and called upon the FDA and other regulatory
agencies to allow professional societies to foster epidemiological
studies.
The only study suggesting a possible link was published in February
1996. 15 Hennekens et al. retrospectively reviewed a large cohort
of 395 543 health professionals and found 10 830 women who reported
breast implants and 11 805 who reported connective-tissue diseases
between 1962 and 1991. The relative risk of any connective-tissue
disease among those reporting implants was 1.24 (95% CI, 1.08-1.41;
P = 0.0015). This indicated a small, but significant, increase
in the risk of connective-tissue disease, but provided reassuring
evidence against silicone implants being a large-scale hazard.
The results fell within the 95% confidence limits of the other
two major studies. The authors stress that biases from self-reporting
of symptoms (questionnaires were sent to the women after the publicity
surrounding the FDA ban) or a higher participation rate in women
with such diseases must be considered as alternative explanations
for their results.
Relationship to breast cancer
In a population-based non-concurrent cohort-linkage study of 11
676 women in Alberta, Canada, who underwent cosmetic breast augmentation
from 1973 to 1986, Berkel et al. found that 41 women with implants
had subsequently developed breast cancer. 16 By comparing these
women to a cohort of women who had a first primary breast cancer
diagnosed between 1973 and 1990, and by applying calendar-year-specific
incidence rates of breast cancer, the expected number of breast
cancer cases in the implant cohort was 86.2. The standardised
incidence ratio was thus 47.6%, significantly lower than expected
( P < 0.01). They concluded that women with silicone breast
implants have a lower risk of breast cancer than the general population.
In a reanalysis of the data used by Berkel et al., Bryant and
Brasher performed multiple estimates of the standardised incidence
ratios on the basis of differing study-eligibility dates, indication
periods and types of breast cancer (invasive or invasive plus
in situ ). 17 They found substantial differences in the numbers
of person-years at risk, resulting in higher standardised incidence
ratios than in the original analysis, and concluded that the risk
of women with silicone breast implants developing breast cancer
was not higher or lower than in the general population.
Summary
Silicone breast implants have a low incidence of mechanical problems
or leakage (about 1.5%).
Silicone breast implants do not increase the risk of breast cancer.
Three large and scientifically sound studies confirm that there
is no strong link between silicone breast implants and connective-tissue
diseases or symptoms.
Medicolegal settlements in the United States
In view of these findings, it must be asked how silicone breast
implants were found wanting and how their main manufacturer was
reduced to bankruptcy? The answer lies in the medicolegal settlements
and judgments made against the company in the United States (
Box 3). The United States legal processes in the breast implant
trials exemplified a growing divergence between science and the
law, and the use and abuse of expert witnesses in an adversarial
legal system. 20 In just four years, the litigation bar in the
United States demolished the largest manufacturer of medical silicone
products.
The future
So far, litigation has been aimed largely at the manufacturers
of breast implants, but if they were unable to pay could individual
surgeons who performed the implants be sued?
What transpired in United States courtrooms and in the United
States media, at least at the time of the FDA ban, were judgments
allegedly based on anecdote and speculation. 16 Anecdote and fear
prevailed over science and were successful. I only hope that Australian
courts will admit reasoned scientific evidence and that settlements,
if any, are commensurate with damages and not excessive. In Australia,
we must maintain scientific objectivity, so that silicone continues
to be available for implantation in its many forms.
References
Commonwealth Department of Human Services and Health.
Breast implant information booklet. Canberra: AGPS, 1995.
Duffy MJ, Woods JE. Health risks of failed silicone gel breast
implants: a 30 year clinical experience. Plast Reconstr Surg 1994;
94: 295-299.
Van Nunen SA, Gatenby PA, Basten A. Postmammoplasty connective
tissue disease. Arthritis Rheum 1982; 25: 694-697.
Kumagai Y, Shiokawa Y, Medsger TA, et al. Clinical spectrum of
connective tissue disease after cosmetic surgery. Arthritis Rheum
1984; 27: 1-12.
Spiera H. Scleroderma after silicone augmentation mammoplasty.
JAMA 1988; 260: 236-238.
Varga J, Schumacher R, Jimenez SA. Systemic sclerosis after augmentation
mammoplasty with silicone implants. Ann Intern Med 1989; 111:
377-383.
Englert H, Morris D, March L. Scleroderma and silicone gel breast
prostheses -- the Sydney study revisited. Aust N Z J Med 1996;
26: 349-355.
Brooks PM. Silicone breast implantation: doubts about the fears.
Med J Aust 1995; 162: 432-434.
Reilly PA. Fibromyalgia in the workplace -- a management problem.
Ann Rheum Dis 1993; 52: 249-251.
Englert HJ, Brooks P. Scleroderma and augmentation mammoplasty
-- a causal relationship? Aust N Z J Med 1994; 24: 74-80.
Gabriel SE. Risks of connective-tissue diseases and other disorders
after breast implantation. N Engl J Med 1994; 330: 1697-1702.
Medical Devices Agency. Silicone implants and connective tissue
disease. London: Department of Health, 1995.
Sanchez-Guerrero J, Colditz GA, Karlson EW, et al. Silicone breast
implants and the risk of connective-tissue diseases and symptoms.
N Engl J Med 1995; 332: 1666-1670.
American College of Rheumatology. Issues Statement on Silicone
Breast Implants, 24 October 1995 [press release].
Hennekens CH, Lee I-M, Cook NR, et al. Self-reported breast implants
and connective-tissue diseases in female health professionals.
A retrospective cohort study. JAMA 1996; 275: 616-621.
Berkel H, Birdsell DC, Jenkins H. Breast augmentation: a risk
factor for breast cancer? N Engl J Med 1992; 326: 1649-1653.
Bryant H, Brasher P. Breast implants and breast cancer-- reanalysis
of a linkage study. N Engl J Med 1995; 332: 1535-1539.
Nocera J. Fatal litigation. Fortune 1995 Oct 16; No 20: 46-66.
Nocera J. Fatal litigation. Fortune 1995 Oct 30; No 21: 137-158
Angell M. Evaluating the health risks of breast implants: the
interplay of medical 1513-1518.
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