Plasma Organochlorine Levels and the Risk of Breast Cancer

Reviewers: John Han-Chih Chang, MD and Ken Blank, MD
Source: TheNew England Journal of Medicine -- October 30, 1997 -- Volume337, Number 18

Several correlative pieces of data indicate that environment playsan important role in the etiology ofbreastcancer. Included in this data is the fact that daughters of womenwho emigrate assume the breast cancer risk of the new country. Thequestion which has stymied researchers and physicians for years is--what in the environment causes breast cancer? One postulate is thatthe level of environmental estrogens such as organocholines inpesticides and industrial chemicals may cause breast cancer. The twomost commonly used organcholines are2,2,-bis(p-chlorylphenyl)-1,1,1-trichlorethane (DDT) and certainpolychlorinated biphenyls (PCBs).

In some animal models DDT was found to promote the growth ofbreast cancer. The metabolites of these two compounds haveestrogen-like activity and often linger in the human body-particularly the fat tissue - for long periods of time. A study inthe 1970s found that the large majority of nursing mothers haddetectable levels of PCB and DTT in their breast milk, even thoughDDT was banded from usage in the United States in 1975.

The association of these two substances with human breast canceris unclear. Several small studies indicate that women with breastcancer have a higher levels of PCB and DTT than controls. However,other studies found the opposite: that there was no associationbetween PCB and DTT levels and breast cancer. As reported in theOctober 30, 1997 New England Journal of Medicine, Hunter et al fromthe Harvard Medical School and Mount Sinai Hospital, New York,undertook a study and in which the blood samples of 240 breast cancerpatients were prospectively collected and measured for levels of bothDDE and PCBs. These levels The level of DDE was lower among breastcancer patients compared to controls. Additionally- and surprisingly- those women with the highest level of DDE and PCB had the lowestrisk of breast cancer. This report concludes that these DDT and PCBare not associated with beast cancer.