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National Cancer Institute
Breast Implant Study
In 1992, researchers at
the National Cancer Institute (NCI) initiated a study on the long-term
health effects associated with silicone breast implants. It is estimated
that between 1.5 million and 2 million women in this country have had
breast implants since they first appeared on the market in 1962.
One of the longest and
largest studies to date on the health effects of implants, the NCI report
involves 13,500 women with an average follow-up time of 13 years. Most
previous investigations have looked at the health effects over a shorter
time period, typically less than 10 years, and have been too small to
evaluate uncommon diseases.
In addition, earlier
reports did not include detailed information about types of implants or
risk factors affecting health, such as medical history, screening
practices, and lifestyle behaviors all of which are included in the current
study.
Another unique feature
of the NCI study is that the investigators compared the health risks of the
implant patiënts to both the general population and other plastic surgery
patiënts. Prior reports have used only the general population as a
comparison group.
The purpose of the NCI
study is to evaluate the effect of implants on the risk of:
·
Developing breast cancer;
·
Developing cancers other than
breast;
·
Dying from all causes of mortality;
and
·
Developing connective tissue disorders.
The results will be
published in various scientific journals. As the publications appear in the
literature, the findings will be summarized at the end of this fact sheet.
Background
Breast implants were
first marketed in the early 1960s, before the 1976 Medical Device
Amendments to the Food, Drug and Cosmetic Act required that medical devices
be shown to be safe and effective. Silicone was initially assumed by
manufacturers to be biologically inactive and, therefore, to have no
harmful effects. However, cases of connective tissue disorders and cancers
were reported in several short-term studies.
Because there were few
reports on the long-term safety of implants, in 1992, the Food and Drug
Administration (FDA) restricted the use of silicone gel breast implants to
controlled clinical trials of women seeking breast reconstruction. That
year, Congress also directed the National Institutes of Health to undertake
a large follow-up study to assess the long-term health effects of exposure
to silicone breast implants.
Types of Implants
Implants are soft
silicone sacs or shells, inflated with either saline solution (salt water)
or a synthetic silicone gel. Until the FDA ban in 1992, 90 percent to 95
percent of the implants contained the silicone gel because it had a more
pleasing look and feel than the saline-filled implants. Since the 1992 ban,
90 percent to 95 percent of the implants have been saline-filled.
Currently, it is not known how many women have silicone vs. saline
implants, but women with both types are included in the NCI study.
Previous Studies
About 80 percent of
breast implants in the United States are for cosmetic reasons and 20
percent for breast reconstruction after breast cancer surgery. The majority
of previous studies have focused on women who received implants for
cosmetic reasons.
1.
Breast Cancer Risk
A number of previous studies have evaluated the relationship between
breast implants and subsequent breast cancer risk. Most have shown that the
risk of developing breast cancer is less among women with implants compared
to women without implants. In several of the studies, the size of the
reduced risk was as much as 50 percent to 60 percent. However, the vast
majority did not have enough detailed information on patiënt
characteristics that could affect the development of breast cancer, and had
follow-up times of less than 10 years.
2. Stage at Diagnosis of Breast
Cancer
Some clinical studies have suggested that women with breast implants
have more advanced breast cancer at diagnosis than women without breast
implants. This is because implants have been reported to decrease the
ability to detect breast lesions, with either clinical examination or
mammography. However, in two larger epidemiologic studies, there did not
appear to be differences in stage at diagnosis or survival rates among the
two groups.
3.
Mortality
No prior studies have evaluated all causes of mortality of breast
implant patiënts but, instead, have limited their analyses to mortality
from breast cancer. Compared to the general population, no increased risk
in breast cancer mortality for implant patiënts was observed.
4.
Types of Implant
Because earlier reports did not include detailed information about
the types of implants, an evaluation of the effect of the implant type on
the health risks of the patiënts has not been possible.
5.
Connective Tissue Disorders
Anecdotal reports have suggested increased risks of certain
connective tissue disorders, including scleroderma, systemic lupus
erythematosus, rheumatoid arthritis, and Sjogren's syndrome. The size of
the studies, however, has not been large enough to draw any definite
conclusions.
6. Women who receive implants for
breast reconstructive surgery
One small study reported no increase in the development of second
primary breast cancer in women with silicone implants following mastectomy
compared to women who received mastectomies without implants. The small
size of the study, however, limits the conclusions.
Note: Any study of the risks of breast cancer or other cancers with
women who receive reconstructive implants is more complicated than one
involving women with cosmetic implants because it needs to take into
account the effects of different breast cancer treatments. A study with
breast cancer patiënts would best be done in the context of a clinical
trial where comparisons can be made between women who choose to have
reconstruction and those who do not, but who otherwise have received
identical treatments.
patiënt Population
in the NCI Study
The participants
include 13,500 women who had implant surgery for cosmetic reasons in both
breasts before 1989. 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 or neck, were identified. All
participants were from 18 plastic surgery practices in six geographic areas
(Atlanta, Ga.; Birmingham, Ala.; Charlotte, N.C.; Miami and Orlando, Fla.;
and Washington, D.C.). The practices were chosen because the plastic
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 health effects of the implant patiënts were also compared to
the general population.
Half (49.7 percent) of
the participants received silicone gel implants, 34.1 percent double lumen
implants, (these have two shells; the inner sac is filled with silicone gel
and the outer one with saline), 12.2 percent saline-filled implants, 0.1
percent other types of implants, and 3.8 percent unspecified types of
implants.
The study participants
had cosmetic surgery between 1962 and 1988 during a time 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 silicone
gel composition. There were no women included in the study who received
implants following a diagnosis of breast cancer.
Study Design
The medical records
from the plastic surgery practices were reviewed to identify patiënts who
were eligible for the study. For eligible patiënts, trained medical records
abstractors collected information about the surgical procedures, the type
of implant, any complications, and factors which might affect health
status, such as weight or medical history.
patiënts were then
traced through a variety of sources. Living subjects were asked to complete
a mailed questionnaire to collect information about their health status,
including whether they had subsequent plastic surgery, as well as lifestyle
factors that could affect their health (menstrual, pregnancy, and
breast-feeding history, weight, hormone use, cigarette smoking, alcohol
consumption, and medical history). Extensive data on the potential
short-term (rupture) and longer-term complications (cancer, connective
tissue diseases, symptoms of connective tissue disease) were also obtained
through the questionnaire.
No clinical
examinations were done on the living patiënts for this study. Attempts were
made to verify patiënt reports of cancer and connective tissue diseases
from the medical records of physicians who had diagnosed or treated these
diseases. To verify the causes of death, death certificates were collected
for the patiënts who had died.About 80 percent of the original 13,500
implant patiënts and 4,000 controls were successfully traced. About 70
percent of those traced as alive completed the questionnaires. These
percentages are similar to other comparably designed epidemiologic studies.
Special Issues
Because of the highly
controversial and political nature of the study, maintaining objectivity
was a particularly important issue. The following
steps were taken to ensure scientific objectivity:
·
The study was funded entirely by the
government, not by plastic surgeons, implant manufacturers, or other
special interest groups.
·
Government scientists, not
manufacturers of implants or plastic surgeons, designed and provided
scientific oversight for the study.
·
To participate in the study, plastic
surgeons had to agree to allow investigators to see all of their records,
not just records for selected patiënts. The investigators obtained detailed
information on factors which could affect health status.
·
Information gathered through the
participant questionnaire about diseases such as cancer or connective
tissue disorders was confirmed by the medical records of oncologists,
rheumatologists, and other physicians who had seen the study respondents
for these illnesses.
·
Death certificates were collected
for the patiënts identified as deceased to verify the causes of death.
·
Scientific oversight for the study
has been provided by NCI's Board of Scientific Counselors and its Breast
Implant Study Advisory Panel, a multidisciplinary panel of academic
scientists, including oncologists, plastic surgeons, rheumatologists, and
epidemiologists, as well as patiënt advocates and consumer representatives.
The panel meets regularly with NCI researchers to address issues involving
data analysis and interpretation, and reports to NCI's Board of Scientific
Counselors.
·
A number of professional plastic
surgery organizations, including the American Society of Plastic and
Reconstructive Surgeons and the American Aesthetic Society, were consulted
to help identify long-standing practices in which at least 500 cosmetic
operations were done prior to 1989 and in which the surgeons retained
complete records and were willing to give the researchers complete access
to them. The NCI investigators performed their own review of the patiënt
records.
Investigators
Louise A. Brinton,
Ph.D., is chief of the Environmental Epidemiology Branch in NCI's Division
of Cancer Epidemiology and Genetics (DCEG). Additional NCI investigators
are Jay H. Lubin, Ph.D., and Robert N. Hoover, M.D., also from DCEG. S.
Lori Brown, Ph.D., is a research scientist from the FDA's Center for
Devices and Radiological Health in Rockville, Md. Theodore Colton, Sc.D.,
from the Department of Epidemiology and Biostatistics at the Boston
University School of Public Health in Massachusetts, was under contract
with the study team, as was Mary Cay Burich from Abt Associates Inc., in
Chicago, who assisted with specific data collection tasks.
Results/Publications
·
The authors showed that other
plastic surgery patiënts are a more appropriate comparison group than women
in the general population for studies of the health effects of breast
implants.
In analyzing the data from the 7,447 breast implant patiënts and
2,203 patiënts with other types of plastic surgery, there were no
differences between the two groups with respect to family income, number of
pregnancies, alcohol consumption, cigarette smoking, histories of previous
gynecologic operations, or operations for benign breast disease.
Reference:
Brinton LA, Brown SL, Colton T, et al. Characteristics of a Population of Women
with Breast Implants Compared with Women Seeking Other types of Plastic
Surgery. Plastic and Reconstructive Surgery
2000;105(3):919-27.
·
The NCI researchers found no
association between breast implants and the subsequent risk of breast
cancer
In addition, they found no link between breast cancer risk and
number of years of follow-up, nor with any particular type of implant. They
did, however, see a shift toward somewhat later detection of breast cancers
among the implant patiënts compared to the controls. Even though the
differences were not statistically significant, there were consistently
smaller percentages of in situ (early-stage) cancers among the implant
patiënts. However, there was no significant difference in breast cancer
mortality between the implant and comparison patiënts.
Reference:Brinton
LA, Lubin JH, Burich MC, et al. Breast Cancer Following Augmentation Mammoplasty (United States). Cancer Causes & Control 2000; 11(9):819-827.
·
Women with implants were not at
increased risk for most cancers with the exception of respiratory and brain
cancers. The
significance of the increased risks is not clear.
NCI researchers did not find increased risks for cancers of the
stomach, large intestine, cervix, uterus, ovary, bladder or thyroid.
Likewise, neither connective tissue nor immune system cancers such as soft
tissue sarcomas, lymphoma, and multiple myeloma, developed at higher rates.
These cancers were previously linked to implants in smaller studies. The
cancer rates for brain and respiratory cancers, however, were two to three
times greater in the implant patiënts compared to other plastic surgery patiënts;
only the rates of respiratory cancers reached statistical significance. The
significance of the findings is not clear. It is possible that the higher
risks observed for respiratory and brain cancers are not related to
exposure to silicone, but are due to either chance findings or to factors
common to women who choose to have implants.
Reference:
Brinton LA, Lubin JH, Burich MC, et al. Cancer Risk at Sites Other than Breast
Following Augmentation Mammoplasty. Annals of
Epidemiology May 2001; 11(4):248-256.
·
Women with implants were not at
increased risk for most causes of death compared to the control group. The
exceptions were deaths from suicide, and brain and respiratory cancers, but
the significance of these increased risks is not clear.
The researchers found that nearly every cause of death, including
all cancers, circulatory and digestive system diseases, and endocrine,
nutritional, metabolic and immune diseases, was decreased among implant
patiënts compared to the general population. However, implant patiënts were
three times more likely to die from respiratory tract cancer, two to three
times more likely to die from brain cancer, and four to five times more
likely to die from suicide than the comparison group; only the rates for
respiratory cancers reached statistical significance. It is possible that
these higher risks are not related to exposure to silicone, but are due to
either chance findings or to factors common to women who choose to have
implants.
Reference:
Brinton LA, Lubin JH, Burich MC, et al. Mortality Among Augmentation Mammoplasty
patiënts. Epidemiology May 2001;12(3):321-326.
·
Women with breast implants were not
at an increased risk for connective tissue disorders when their records
were reviewed by two independent rheumatologists who did not know if the
women had an implant or not
According to initial reporting by an implant patiënt questionnaire,
there appeared to be a two fold increased risk for developing rheumatoid
arthritis, scleroderma, systemic lupus erythematosus, and Sjogren's
syndrome in this population. NCI researchers were able to access only
34-40% of these patiënts' records who reported being diagnosed with a
connective tissue disorder. When these records were reviewed by two
independent, board-certified rheumatologists who did not know if the
patiënt had an implant or not, the rheumatologists found between 17-30% of
the diagnoses likely. As a result, the risk for developing a connective
tissue disorder due to breast implants, while still somewhat elevated,
became statistically non-significant. Further research including records
linkage, standardized diagnostic criteria for rheumatoid disorders, and
clinical exams, is needed to understand if a relationship exists.
Reference: Brinton LA, Buckley LM, Dvorkina O, et al. Risk of Connective Tissue
Disorders among Breast Implant patiënts. American Journal of
Epidemiology; 2004;160; 619-627.
Related Links:
NCI news web site for press releases about breast implants: Oct. 2,
2000 for breast implants and breast cancer risk; April 23, 2001 for press
releases on risk of other cancers; April 27, 2001 for causes of mortality
release. http://www.cancer.gov
FDA Web site on breast implants: http://www.fda.gov/cdrh/breastimplants/.
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