Combined Studies Show No Association of Exposure to DDE and PCBs with Breast Cancer Risk

Gwen Collman, Ph.D., NIEHS
Jo L. Freudenhein, Ph.D., SUNY Buffalo; R01CA/ES62995
Kathy J. Helzlsouer, MD, Johns Hopkins University; R01CA/ES62988
Mary Wolff, Ph.D., Mount Sinai Medical Center; R01CA/ES62951
Tongzhang Zheng, MD, Yale University School of Medicine; R01CA/ES62986
David J. Hunter, MD, Brigham and Women's Hospital; R01CA/ES62984M

Background: Breast cancer in women is a serious and pervasive illness in the United States. Overall, one in nine women will develop breast cancer at some point in her life. In some areas of the country, the risk is higher, most notably in the northeastern United States. Some epidemiologic studies have shown associations between DDE (the major metabolite of the banned insecticide DDT) and PCBs (once used in industry) and breast cancer. Most of the positive studies have shown only modest increased risks while many other studies reported no association at all. To investigate this issue more vigorously, the National Cancer Institute and the National Institute of Environmental Health Sciences joined forces in 1993 to fund five large studies. All five of these studies have reported finding no association overall; however, suggestions of effects were seen in some subgoups. To investigate this matter further and to increase the power of the individual studies, the results were combined and reanalyzed with controlled methodologies.

Advance: The combined study consisted of 1,400 case patients with breast cancer and 1,642 controls. The results do not support an association of breast cancer risk with serum/plasma levels of PCBs or DDE. The risk of breast cancer was equivalent in women who had the highest PCB and DDE levels to women with the lowest levels.

Implication: The lack of an association between PCBs and DDE and breast cancer risk does not rule out the possibility that specific PCB congeners, pesticides, or other environmental contaminants may be associated with breast cancer. However, body burdens of PCBs and DDE are not likely to explain the high rates of breast cancer in the northeastern United States. Further research on other possible environmental risk factors is needed and is currently underway.

Publication: Laden F, Collman G, Iwamoto K, Alberg AJ, Berkowitz GS, Freudenheim JL, Hankinson SE, Helzlsouer KJ, Holford TR, Huang HY, Moysich KB, Tessari JD, Wolff MS, Zheng T, Hunter DJ. 1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene and polychlorinated biphenyls and breast cancer: combined analysis of five U.S. studies. J Natl Cancer Inst. 2001 May 16;93(10):768-76.