Subject: THE TRUTH ABOUT BREAST CANCER--PART 4 .
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THE TRUTH ABOUT BREAST CANCER--PART 4
Late last month the NEW ENGLAND JOURNAL OF MEDICINE (NEJM)
published a study (by David J. Hunter) comparing the levels of
DDE and PCBs in the blood of two groups of women, one group with
breast cancer, the other without.[1] The Hunter study failed to
find a positive relationship between breast cancer and DDE or
PCBs in the blood. DDE is a breakdown product of the
organochlorine pesticide DDT, which was banned in the U.S. in the
mid-1970s; PCBs are a group of 209 chlorinated industrial
chemicals, also banned in the U.S. The Hunter study is the
largest of its kind to date, comparing 236 pairs of women for DDE
and 230 pairs for PCBs.
The NEW ENGLAND JOURNAL OF MEDICINE put a far-reaching title on
the new study: "Plasma Organochlorine Levels and the Risk of
Breast Cancer." (Plasma is the part of the blood that contains
fat-soluble chemicals such as organochlorines.) The title seemed
to suggest that a study of two chemicals --DDE and PCBs --could
tell us something definitive about all of the 15,000 different
organochlorine compounds in relation to breast cancer.
In case we missed the message, the editors of the JOURNAL
provided an editorial that spelled it out. The editorial, by
Stephen H. Safe, a Texas researcher whose work is often funded by
the Chemical Manufacturers Association, had a slightly different
though equally far-reaching title: "Xenoestrogens and Breast
Cancer." (Xenoestrogens are industrial chemicals that interfere
with normal sex hormones such as estrogen.)
Dr. Safe's editorial in NEJM began, "Chemophobia, the
unreasonable fear of chemicals, is a common public reaction to
scientific or media reports suggesting that exposure to various
environmental contaminants may pose a threat to health." Surely
this is an odd message from a scientist. He is saying, if you
fear chemicals because scientific reports indicate that they
might harm your health, you are suffering from an irrational
phobia. Perhaps Dr. Safe did not write the editorial in his
capacity as a scientist.
Dr. Safe concludes his chemophobia editorial saying it is time we
all stopped worrying about organochlorines and breast cancer. He
writes, "The results of Hunter along with those of other recent
studies should reassure the public that weakly estrogenic
organochlorine compounds such as PCBs, DDT and DDE are not a
cause of breast cancer."[2] Estrogenic organochlorine compounds
such as DDT, DDE and PCBs are not a cause of breast cancer. Case
closed.
If we still didn't get the point, Gina Kolata of the NEW YORK
TIMES interviewed Dr. Safe, giving him an opportunity to amplify
his message. Dr. Safe told Ms. Kolata it is time to quit
researching the relationship between organochlorine chemicals and
breast cancer: "For advocates [of the idea that the two are
connected], it's never ending. But for other people, there may be
times when we want to spend our money on other things," Dr. Safe
said.[3] No more research needed. Case closed.
Three days later in the Sunday TIMES, Gina Kolata delivered the
message once again, summarizing the Hunter study this way: "One
more environmental scare bit the dust last week as scientists
from the Harvard School of Public Health reported that their
large and meticulous study found no evidence that exposure to the
chemicals DDT and PCB's [sic] are linked to breast cancer."[4]
Another scare bit the dust. Case closed.
Including the recent Hunter study, there are now 11 published
studies of organochlorine compounds (DDE, PCBs, methoxychlor,
beta-hexachlorobenzene, and chlordane --the last 3 being
pesticides) in relation to breast cancer. Four studies,
including the largest two of the 11, have shown no relationship
between DDE, PCBs and breast cancer.[1,5,6,7] Six smaller
studies have indicated a positive relationship, suggesting that
some organochlorines may be implicated somehow in breast
cancer.[8,9,10,11,12,13] One additional study was equivocal,
subject to differing interpretations.[14]
The equivocal study was by led by Nancy Krieger, who examined DDE
and PCB levels in the blood of 150 women with breast cancer and
150 women without breast cancer. The 300 women were chosen to
represent racial/ethnic groups: 100 whites, 100 African-Americans
and 100 Asian-Americans. Taken together, the 300 women showed no
statistically-significant relationship between DDE, PCBs and
breast cancer. However, when the racial/ethnic groups were
studied individually, the whites and the African-Americans with
breast cancer showed elevated levels of DDE in the blood,
compared to whites and African-Americans without breast
cancer.[14] Asian and recently-immigrated Asian-American women
tend to have a much lower incidence of breast cancer than white
Americans, perhaps because of a protective effect from their
diet.[15,16] Omitting the Asian-Americans from the Krieger study
essentially reverses the study's conclusions.
Thus out of 11 studies, 4 are negative and 7 show elevated levels
of organochlorines of one kind or another in tissues of women
with breast cancer. One of those seven were not statistically
signficant. Is it time to close the book on this inquiry?
Stephen Safe and Gina Kolata obviously want us to think so. Dr.
Safe and Ms. Kolata both try to make us believe that recent work
has revealed that breast cancer can be completely explained by
"known risk factors." Listen to Dr. Safe: "Robbins and coworkers
recently showed that the high incidence of breast cancer in women
from the San Francisco Bay area can be accounted for by known
risk factors, including parity [how many children they've had],
age at first full-term pregnancy, months of breast-feeding, age
at menopause, age at menarche [when a woman's period commences],
and alcohol consumption."[2] Ms. Kolata takes the argument even
further: "Dr. Hunter said that perhaps it was time to question
the assumption that much breast cancer is caused by unknown
environmental agents. A recent study, for example, found that the
high rate of breast cancer in the San Francisco Bay area can be
completely attributed to known risk factors like a woman's age
when she start to menstruate, has a first child, and when she
begins menopause."
Dr. Safe and Ms. Kolata both make it sound as if this new study
of women in San Francisco has revealed that all breast cancer can
be explained by "known risk factors." If true, this is important
news.
In fact the Robbins study of women in the San Francisco Bay area
did not even try to explain the origins of all breast cancer.[17]
Robbins observed that white women near San Francisco Bay have a
14% higher incidence of breast cancer than the national average
(and African-American women in the Bay area are 10% above the
national average), and he set out to see if he could explain the
14% and 10% increases. He and his coworkers found that women in
San Francisco tend to have fewer children, have them later in
life, breast feed them less, and so forth, thus explaining the
14% and 10% increases by "known risk factors." The 50% to 70% of
breast cancer that can't be explained anywhere else in the U.S.
also can't be explained in San Francisco --despite the false
impression that Dr. Safe and Ms. Kolata managed to create.
What about Stephen Safe's conclusion (amplified by Ms. Kolata),
that, based on four negative studies of DDE and PCBs, we should
stop trying to find the links between environmental estrogenic
chemicals and breast cancer?
Stephen Safe knows that DDE is not estrogenic. DDT is
estrogenic, but DDE is not. DDE is a potent anti-androgen (it
blocks the action of male hormones).[18] DDE DOES interfere with
sex hormones, but it doesn't mimic estrogen and there's no good
reason to think it would make a major contribution to breast
cancer. Likewise, many PCBs are not estrogenic --on the
contrary, they are ANTI-estrogenic. Dr. Safe's own research has
shown this again and again.[19] Thus there is no good reason to
think that DDE and a randomly-selected group of mixed PCBs will
cause breast cancer. Listen once more to Dr. Safe's editorial
(titled "Xenoestrogens and Breast Cancer"). He writes, "The
results of Hunter along with those of other recent studies should
reassure the public that weakly estrogenic organochlorine
compounds such as PCBs, DDT and DDE are not a cause of breast
cancer." But DDE is not estrogenic, and neither are many PCBs.
This is a false argument and Dr. Safe --and the editors of the
NEW ENGLAND JOURNAL OF MEDICINE --know it.
There are good, strong reasons to think that many
estrogen-mimicking chemicals, some of them organochlorines, might
be associated with breast cancer, and these should be carefully
examined. But DDE and mixed PCBs are not in that category. They
have been studied because they are convenient to study, not
because they are particularly estrogenic. When Stephen Safe tells
Gina Kolata we might want to end research on organochlorines and
breast cancer based on studies of DDE and mixed PCBs, Dr. Safe is
sounding like a camp follower of the Chemical Manufacturers
Association, not like a scientist.
--Peter Montague
(National Writers Union, UAW Local 1981/AFL-CIO)
===============
[1] David J. Hunter and others, "Plasma Organochlorine Levels and
the Risk of Breast Cancer," NEW ENGLAND JOURNAL OF MEDICINE Vol.
337, No. 18 (October 30, 1997), pgs. 1253-1258. Studied 236
pairs of women for DDT levels and 230 pairs of women for PCB
levels.
[2] Stephen H. Safe, "Xenoestrogens and Breast Cancer," NEW
ENGLAND JOURNAL OF MEDICINE Vol. 337, No. 18 (October 30, 1997),
pgs. 1303-1304.
[3] Gina Kolata, "Study Discounts DDT Role in Breast Cancer," NEW
YORK TIMES October 30, 1997, pg. 26.
[4] Gina Kolata, "DDT and Breast Cancer," NEW YORK TIMES November
2, 1997, pg. 2.
[5] M. Unger and others, "Organochlorine compounds in human
breast fat from deceased with and without breast cancer in a
biopsy material from newly diagnosed patients undergoing breast
surgery," ENVIRONMENTAL RESEARCH Vol. 34 (1984), pgs. 24-28.
Studied 32 cases and 56 controls.
[6] Pieter van't Veer and others, "DDT (dicophane) and
postmenopausal breast cancer in Europe: case-control study,"
BRITISH JOURNAL OF MEDICINE Vol. 315 (July 12, 1997), pgs. 81-85.
Studied 265 cases and 341 controls.
[7] Lizbeth Lopez-Carrillo and others,
"Dichlorodiphenyltrichloroethane Serum Levels and Breast Cancer
Risk: A Case Control Study from Mexico," CANCER RESEARCH Vol. 57
(September 1, 1997), pgs. 3728-3732. Studied 141 cases & 141
controls; 562 ppb for cases, 505 for controls, but not
statistically significant.
[8] Frank Falck, Jr. and others, "Pesticides and Polychlorinated
Biphenyl Residues in Human Breast Lipids and Their Relation to
Breast Cancer," ARCHIVES OF ENVIRONMENTAL HEALTH Vol. 47 No. 2
(March/April, 1992), pgs. 143-146. Studied 20 cases and 20
controls. A dose-response relationship was observed.
[9] Mary S. Wolff and others, "Blood Levels of Organochlorine
Residues and the Risk of Breast Cancer," JOURNAL OF THE NATIONAL
CANCER INSTITUTE Vol. 85, No. 8 (April 21, 1993), pgs. 648-652.
Studied 58 cases and 341 controls. A dose-response relationship
was observed.
[10] Mirjana V. Djordjevic and others, "Assessment of chlorinated
pesticides and polychlorinated biphenyls in adipose breast tissue
using a supercritical fluid extraction method," CARCINOGENESIS
Vol. 15, No. 11 (1994), pgs. 2581-2585. Found elevated levels of
DDE, PCBs, chlordane, oxychlordane and transnonachlor in breast
tissue of 5 women with breast cancer vs. 5 women without rhe
disease.
[11] H. Mussalo-Rauhamas and others, "Occurrence of
Beta-Hexachlorocyclohexane in Breast Cancer Patients," CANCER
Vol. 66, No. 10 (November 15, 1990), pgs. 2124-2128. Studied 44
cases and 33 controls. Found that Finnish women with elevated
levels of beta-hexachlorocyclohexane, a breakdown product of the
pesticide Lindane, in their breast tissue had a 10-fold increased
risk of breast cancer. See also, Rosemary Steinmetz and others,
"Novel Estrogenic Action of the Pesticide Residue
Beta-Hexachlorocyclohexane in Human Breast Cancer Cells," CANCER
RESEARCH Vol. 56 (December 1, 1996), pgs. 5403-5409.
[12] Eric Dewailly, "High Organochlorine Body Burden in Women
With Estrogen Receptor-Positive Breast Cancer," JOURNAL OF THE
NATIONAL CANCER INSITUTE Vol. 86, No. 3 (February 2, 1994), pgs.
232-234. Studied 20 cases and 17 controls. Found a nine-fold
increased risk of breast cancer among women with
estrogen-responsive breast tumors
[13] M. Wassermann and others, "Organochlorine Compounds in
Neoplastic and Adjacent Apparently Normal Breast Tissue,"
BULLETIN OF ENVIRONMENTAL CONTAMINATION & TOXICOLOGY Vol. 15, No.
4 (1976), pgs. 478-484. Organochlorine compounds (DDT and PCBs)
were higher in 9 breast cancer patients than in 5 controls, and
in cancer patients the cancerous tissue contains significantly
more organochlorines than adjacent normal tissues.
[14] Nancy Krieger and others, "Breast Cancer and Serum
Organochlorines: A Prospective Study Among White, Black and Asian
Women," JOURNAL OF THE NATIONAL CANCER INSTITUTE Vol. 86, No. 8
(April 20, 1994), pgs. 589-599. In the same issue, see the
editorial, pgs. 572-573 and "DDT and Breast Cancer: The Verdict
Isn't In," pgs. 576-577.
[15] A.H. Wu and others, "Tofu and risk of breast cancer in
Asian-Americans," CANCER EPIDEMIOLOGY, BIOMARKERS AND PREVENTION
Vol. 5, No. 11 (November 1996), pgs. 901-906.
[16] Herman Adlercreutz, "Phytoestrogens: Epidemiology and a
Possible Role in Cancer Protection," ENVIRONMENTAL HEALTH
PERSPECTIVES Vol. 103, Supplement 7 (October 1995), pgs. 103-112.
[17] Anthony S. Robbins and others, "Regional Differences in
Known Risk Factors and theHigher Incidence of Breast Cancer in
San Francisco," JOURNAL OF THE NATIONAL CANCER INSTITUTE Vol. 89,
No. 13 (July 2, 1997), pgs. 960-965.
[18] William R. Kelce and others, "Persistent DDT metabolite
p,p'-DDE is a potent androgen receptor antagonist," NATURE Vol.
375 (June 15, 1995), pgs. 581-585.
[19] For example, see M. Moore, S. Safe, and others,
"Antiestrogenic Activity of Hydroxylated Polychlorinated Biphenyl
Congeners Identified in Human Serum," TOXICOLOGY AND APPLIED
PHARMACOLOGY Vol. 142 (1997), pgs. 160-168.
Descriptor terms: new england journal of medicine; breast
cancer; dde; ddt; pcbs; david j. hunter; studies; estrogen;
organochlorines; stephen h. safe; chemical manufacturers
association; gina kolata; methoxychlor; beta-hexachlorobenzene;
chlordane; nancy krieger;
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