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American Health Foundation
November 10, 2000
Long Island Study Finds
Little Evidence that
Organochlorine Compounds Increase Risk for Breast Cancer
Findings from a hospital-based case-control study
of women from Long Island suggest that increased risk for breast
cancer does not appear to be associated with past exposure to organochlorine
compounds, according to Steven D. Stellman, Ph.D., M.P.H., of the
American Health Foundation (AHF), Valhalla, N.Y., and colleagues.
The lack of association held for both women whose tumors were estrogen
receptor positive, as well as for women whose tumors were estrogen
receptor negative.
The research findings are consistent with the results
of other recent investigations of organochlorine compounds and risk
for breast cancer that have been reported in other regions. “No
single study is definitive; rather, it is the gathering of evidence
from different studies and populations that is necessary to reach
a conclusion about whether these compounds are associated with increased
risk for breast cancer,” said Dr. Stellman. “Other research is under
way on Long Island that is examining environmental exposures to
organochlorine compounds in relation to risk for breast cancer,
and we look forward to the findings from these analyses next year.”
The findings are reported in the November issue
of Cancer Epidemiology, Biomarkers & Prevention.* Collaborating
on the study are: Mirjana V. Djordjevic, Ph.D., Joshua E. Muscat,
Ph.D., and Lin Gong, Ph.D., of AHF; Julie A. Britton, Ph.D., Mount
Sinai School of Medicine; Marc L. Citron, M.D., and Erna Busch,
M.D., ProHEALTH Care Associates, Lake Success, N.Y.; and Margaret
Kemeny, M.D., State University of New York (SUNY) at Stony Brook,
Stony Brook, N.Y. Dr. Stellman is also on the Epidemiology faculty
at the Mailman School of Public Health, Columbia University, N.Y.
Study Design
The study included 232 women who had surgery for
breast cancer (cases) and 323 women who had surgery for non-cancerous
breast disease or for conditions unrelated to the breast (controls).
Of the cases, 199 had invasive breast cancer and 33 had carcinoma
in situ. The women in the control group had had surgeries involving
their gall bladder, removal of lipomas, abdominal hernias, osteoarthritis,
and other conditions unrelated to the breast. The women were treated
between 1994 and 1996. Both groups were similar in education, race,
body mass index (a composite measure of weight and height), age
at first live birth of a child, and county of residence.
The women had received their care at Long Island
Jewish Medical Center, New Hyde Park, N.Y., and North Shore University
Hospital, Manhasset, N.Y., which are the two largest hospitals serving
the Long Island population. Fifty-seven percent of cases (128 women)
and controls (186 women) lived in Nassau or Suffolk County. The
other study participants lived in New York City, primarily in Queens
County. There were no major differences in levels of the organochlorine
compounds and PCBs when the data were compared between women living
in Nassau and Suffolk counties with residents of Queens County.
Also, no significant differences in exposures were seen between
residents of Nassau and Suffolk counties.
The study participants provided adipose (fatty)
tissue obtained at surgery, blood samples, and answered a questionnaire
about their medical and reproductive history, diet, smoking, and
other lifestyle factors. Adipose tissue was used for this analysis
because the fat-soluble organochlorine compounds accumulate and
are stored in body fat for many years. They are excreted very slowly
from the body, making it possible to look for evidence today of
exposures that have occurred over a long period. The adipose tissue
from the breast cancer patients was obtained prior to chemical or
radiation treatment for the disease.
The study focused on 7 organochlorine pesticides
and 14 congeners (types) of PCBs. The organochlorine pesticides
or their products measured were: DDT and two related chemicals,
DDD and DDE (the main breakdown product of DDT in the environment
and in the body); oxychlordane and trans-nonachlor, which are products
of chlordane, a once-common termite treatment; and two pesticides,
 -hexachlorocyclohexane
(-HCH),
and hexachlorobenzene (HCB). PCBs are a group of chemical compounds
found in coolants and lubricants in transformers, capacitors, other
electrical equipment, and some consumer products. DDT was banned
from commercial use in the United States in the 1970s, and PCBs
are no longer permitted in new equipment; however, these highly
persistent compounds are still widely found throughout the environment
and in animals and people. Detectable levels of the organochlorine
pesticides and PCBs were found in all women studied.
Findings
The researchers found that cases and controls had
comparable levels of total organochlorine pesticides and total PCBs
in their adipose tissue, after adjusting for age and body mass.
There was no association between breast cancer risk and levels of
total pesticides or total PCBs.
The researchers found an apparent association with
increased risk for breast cancer only with the PCB congener 183,
which accounts for about 9% of total PCBs. Little is known about
this compound's toxicity, except that it weakly induces enzymes
which may activate some carcinogens. However, no association was
found between risk for breast cancer and the most abundant PCB congener,
153, which is a much stronger inducer and which has also been found
to have estrogenic properties. The meaning of the finding for congener
183 is unclear, and the observation needs to be confirmed in other
studies now in progress. The research team did not confirm a previously
reported association with PCB congener 188.
Future
The researchers continue to follow this study population
and have conducted medical follow-ups of the cases to determine
whether survival or recurrence of breast cancer may be related to
body burden of organochlorines. A questionnaire was mailed to cases
in order to obtain data on lifestyle changes and other patient characteristics
that may have changed since the women were diagnosed with breast
cancer. The women also provided new blood samples to permit study
of changes in levels of organochlorine compounds over time.
The research is part of the Long Island Breast
Cancer Study Project (LIBCSP), which is a group of studies that
are being conducted to investigate environmental contaminants that
may be responsible for the elevated rates of breast cancer in Nassau
and Suffolk counties (Long Island), Schoharie County, N.Y., and
Tolland County, Conn. The LIBCSP is coordinated and funded by the
National Cancer Institute (NCI) and National Institute of Environmental
Health Sciences (NIEHS).
Background
Beginning in the mid-1970s, findings from human
studies began to emerge that suggested that organochlorine compounds
or related compounds and PCBs may be associated with increased risk
for breast cancer, the researchers explained. More recent studies,
however, have not found an association, or only a small suggestion
of a possible association, between exposure to the compounds and
increased risk for breast cancer. A limitation of studies conducted
today though, including the current study, the researchers said,
is that a single measurement of body burden of these compounds made
at the time of diagnosis may not reflect the cumulative lifetime
exposure of individuals or age at exposure, particularly women who
may once have had elevated levels of organochlorine compounds which
were subsequently eliminated from their bodies. More sophisticated
research designs are required which gather comprehensive environmental
exposure histories.
The International Agency for Research on Cancer
(IARC), which reviews and synthesizes evidence on carcinogenicity
of toxic substances and exposures, rates DDT and PCBs as “possible”
or “probable” carcinogens, based upon evidence from animal and human
studies. Furthermore, some of the organochlorine compounds have
been hypothesized to be endocrine disruptors - external agents that
interfere with the role of natural hormones in the body, which suggests
breast cancer as a potential disease outcome.
# # #
* The study is titled “ Breast Cancer Risk in Relation
to Adipose Concentrations of Organochlorine Pesticides and Polychlorinated
Biphenyls in Long Island, New York.” Cancer Epidemiology, Biomarkers
& Prevention is published by the American
Association for Cancer Research.
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