In May 2000, the Medical Devices Agency (MDA) convened an Advisory Group
(consisting of toxicologists, plastic surgeons and a lay representative) to
consider new data on the safety of Trilucent breast implants. The Group
considered the available scientific evidence, made an assessment of the risk to
patients and, based on this assessment, provided advice to
MDA.
Background.
Trilucent breast
implants consist of a silicone elastomer shell with a lipid filler based on
soyabean oil. Over 9000 implants have been implanted into almost 5,000 women in
the UK.
In March 1999 the Medical Devices Agency (MDA) raised concerns
about the lack of long-term safety data on Trilucent breast implants
particularly in relation to the breakdown of the lipid filler. An independent
view on the relevant data was sought from four members of the Department of
Health's Committee of on Toxicity (COT) in March 1999. The COT members raised
two specific concerns at that time: the apparent irritation following rupture
and the apparent increase in levels of degradation products over that upon which
the manufacturer had undertaken their initial safety assessment. They advised
that further data should be obtained to allow a risk assessment to be made. As a
result of these concerns the company voluntarily withdrew Trilucent breast
implants (in March 1999) as a precautionary measure. MDA also issued advice to
the Health Service in the form of MDA Advice Notice (AN1999(01)).
The
Advice Notice stated that in 1999 there was no safety information to suggest
that removal of Trilucent breast implants was indicated but that women should be
advised to seek an immediate clinical consultation if they noticed unusual
breast swelling or inflammation associated with their Trilucent breast
implants.
New information.
After the
March 1999 withdrawal from further sale of Trilucent breast implants, MDA
required the manufacturer to carry out further toxicological testing on the
filler used in Trilucent breast implants. The company has now carried out
chemical analyses which have established the general nature and amount of
breakdown products generated when the filler degrades.
The company had
provided MDA with preliminary data on the levels of various degradation products
measured in samples obtained from both explanted Trilucent breast implants and
retained stock. The explant samples had not been collected under controlled
conditions. The samples from retained implants were taken from devices which had
been stored under the manufacturer's recommended storage conditions.
The
samples from the majority of the explants and retained implants contained
millimolar amounts of at least one type of aldehyde degradation product. Other
samples did not contain amounts greater than the limit of detection of the
measuring technique (10 micromolar). Samples contained millimolar (or greater)
concentrations of intermediate degradation products (hydroperoxydienes). The
company was unable to find a correlation between the concentrations of
degradation products in explants and any known use factors.
The Advisory
Group discussed this new information on 19 May 2000.
The Group
considered that once the production of these degradation products has been
initiated, peroxidation will continue. The concentrations of these degradation
products will increase after sample collection in the absence of adequate
analytical controls. The lack of control on sample handling (especially the time
between explantation and analysis) complicated the assessment of the company's
results.
Although a fraction of the degradation products measured were
accepted as being post-sampling artefacts, the Advisory Group concluded that, at
the concentrations measured, such artefacts would not be sufficient to disregard
the findings of the tests.
Aldehyde degradation
products.
The metabolism of fats in the body produces low
concentrations of degradation products. The degradation products are known to
have a number of biological effects. These include effects on cell proliferation
.Certain degradation products are known to be cytotoxic at micromolar
concentrations; they are also known to be very reactive towards primary amino
groups in proteins and DNA.
Genotoxic
risk.
The Advisory Group agreed that:
The Advisory Group noted that clear evidence of a possible increased
cancer risk in women was unlikely to be available for many
years.
Reproductive toxicity risk.
The
Advisory Group concluded that exposure to genotoxic degradation products
resulting from diffusion of filler through the shell (bleed) or from rupture
posed a potential reproductive toxicity risk whilst the implants were present.
However due to the short half-lives of the degradation products, the Advisory
Group's opinion was that this risk was unlikely to remain after explantation.
The Advisory Group agreed that it was prudent to advise that pregnancy
should be avoided (by use of contraception) until the implants were removed, but
that this precaution would not be necessary after explantation.
In the
Advisory Group's opinion, the possibility of genotoxic degradation products
migrating from implants to breast tissue and milk could not be discounted. It
was therefore prudent to recommend that breast-feeding should be avoided prior
to explantation of Trilucent breast implants.
The Group stressed that
the advice on pregnancy and breast-feeding were precautionary. The advice was
based on their inability to exclude these risks on the data available rather
than any direct evidence for such effects.
Capsule.
The Advisory Group was informed that the capsule formation
around Trilucent breast implants differed from that observed with other breast
implants. The capsule felt like lumps around the implant and the shell appeared
incorporated into the capsule. Although these differences might be due to other
causes (such as the surface texture of the implant), it was the Advisory Group's
opinion that the possible involvement of degradation products in producing this
unusual capsule morphology could not be ignored.
Clinical
issues.
It was the Advisory Group's opinion that women
should be provided with as much information as possible, including the
uncertainties and areas where no information was available. Women had the right
to make an informed choice on whether or not to undergo explantation in response
to the known facts.
The Advisory Group recognised that the majority of
women would not be content with explantation alone but would want replacement
breast implants.
The Advisory Group emphasised that there were other
aspects that needed to be included in a comprehensive package of care provided
to women with Trilucent breast implants. These included: clinical monitoring of
the consequences in women (whether or not they chose to undergo explantation);
possible psychological effects both from the possible loss of the breast and
also worry about long-term consequences.
Recommendations.
The Advisory Group
concluded that:
The Advisory Group stressed that even if Trilucent breast implants were
explanted from women, additional studies would be needed to further characterise
the risks and to provide further information to these women.
The
Advisory Group concluded that there was no data on the safety of implanting
other breast implants subsequent to the removal of Trilucent breast implants and
women needed to be informed that there was no information either way on this
matter.
Last updated : 6 June 2000