Plasma Organochlorine Levels and the Risk of Breast Cancer
Plasma Organochlorine Levels and the Risk of Breast Cancer
ABSTRACT & COMMENTARY
Synopsis: Levels of common organochlorines found in pesticides did not correlate with the development of breast cancer in this case-control study of a subset of women enrolled in the Nurses’ Health Study.
Source: Hunter DJ, et al. N Engl J Med 1997;337:1253-1258.
Epidemiological data strongly suggest that environmental and lifestyle factors are a major cause of breast cancer. Pesticides and industrial chemicals are weakly estrogenic in some assays. Several studies reported higher blood levels of the organochlorine compounds 1, 1-dichloro-2, 2-bis-(p-chlorophenyl)ethylene (DDE), and polychlorinated biphenyls (PCBs) in women with breast cancer as compared to those without breast cancer. Thus, the present study was undertaken to investigate the hypothesis that DDE and PCBs cause breast cancer. Many of these compounds accumulate in the body because they are highly lipophilic and resistant to metabolic degradation. Thus, blood levels are a reliable method to gauge past lifetime exposures. In this study, 240 women who participated in the Nurses’ Health Study and who had given a blood sample and later developed breast cancer were matched to 240 women who did not develop breast cancer. Levels were not significantly lower in the women who later developed breast cancer. Hunter and colleagues conclude that these data do not support the hypothesis that exposure to DDE and PCBs increase the risk of breast cancer.
COMMENT BY SARAH L. BERGA, MD
This study struck me as important because of a heightened sense of fear that many women havethat something in the environment is responsible for breast cancer. While the present study cannot do away with that concern altogether, it certainly ameliorates the sense of panic regarding the compounds DDE and PCBs. In an accompanying editorial, Safe refers to this sense of concern about environmental toxins as "chemophobia."1 Safe et al point out that the average diet contains very low levels of organochlorine compounds and that we ingest much higher levels of naturally occurring estrogenic and antiestrogenic compounds when we eat fruits, nuts, and vegetables. In the public mind, however, phytoestrogens are commonly assumed to be good, and other compounds such as DDE and PCBs, which are synthetic, are commonly thought to be bad. Clearly, this sort of simple-minded logic is unlikely to hold. The truth is, we don’t know what causes breast cancer. Previously, a report on smoking and breast cancer found that smoking increased the risk of breast cancer only in women with polymorphisms of the enzyme NAT2.2 Because of reduced enzyme activity, the women who were "slow acetylators" were slow to rid their bodies of toxic substances and, thus, suffered disproportionately from smoking. In the present study, this mechanism does not seem to play a role in determining the risk of breast cancer because the levels of DDE and PCBs were relatively similar across the groups. However, there may be subsets of women who are more sensitive to any number of putative xenoestrogens because of other differences in their cellular machinery. Although it is far from reassuring to contemplate, it is important to remember how much we don’t know about the pathogenesis of this common cancer. (Dr. Berga is Associate Professor of Obstetrics, Gynecology, Reproductive Services, and Psychiatry, University of Pittsburgh.)
References
1. Safe SH, et al. N Engl J Med 1997;337:1303-1304.
2. Ambrosone CB, et al. JAMA 1996;276:1494-1501.
Gemfibrozil treatment of post-CABG patients with isolated low HDL has been associated with marked reduction in subsequent clinical events despite lack of any demonstrated angiographic benefit.
Which of the following statements about breast cancer is true?
a. Environmental estrogens are the likely cause of the increase in rates of breast cancer.
b. Environmental estrogens have been implicated as a cause of the rising rates of breast cancer.
c. Dietary estrogens are a likely cause of the rise in rates of breast cancer.
d. Our diets are higher in organochlorines than phytoestrogens.
e. There is no reliable method of determining if a woman has or has not been exposed to environmental estrogens because they are rapidly metabolized and cleared from the body.
Subscribe Now for Access
You have reached your article limit for the month. We hope you found our articles both enjoyable and insightful. For information on new subscriptions, product trials, alternative billing arrangements or group and site discounts please call 800-688-2421. We look forward to having you as a long-term member of the Relias Media community.