(NEW HAVEN) -- In the largest such study to date funded by the National Cancer Institute and the National Institute of Environmental Health and Safety, researchers at the Yale Cancer Center did not find a significant relationship between exposure to PCBs or the pesticide DDE, and the risk of breast cancer in women.
In a case-control study of nearly 1,000 Connecticut women, blood serum levels of polychlorinated biphenyls (PCBs) and the organochloride compound DDE were analyzed for an association with breast cancer risk. No significant difference in serum levels was found between the women with breast cancer and the control group. The research was reported in the journal Cancer Epidemiology, Biomarkers and Prevention.
"I am hopeful that this, our most recent and conclusive study, will put to rest the notion that exposure to DDE causes breast cancer," said Tongzhang Zheng, Ph.D., associate professor of epidemiology and public health and the lead author of the study. Based on these results, it is also unlikely that total PCBs have a major impact on the risk of breast cancer."
The question of whether environmental exposure to organochloride compounds (particularly PCBs and DDE) increases the risk of female breast cancer has been debated in recent years, but studies relating PCBs and DDE to breast cancer have produced inconclusive results. Many of the earlier studies, however, were based on a relatively small number of study subjects, and were not designed to take into account potentially important factors that might modify the relationship between PCB and DDE exposures and development of breast cancer.
In this most recent study, a total of 475 breast cancer patients who either had breast-related surgery at Yale-New Haven Hospital or were residents of Tolland County (which has similar breast cancer incidence and mortality rates to New Haven County) comprised the group of cases. The control group of 502 women without breast cancer was randomly selected from among women who had normal tissue or newly diagnosed benign breast disease or normal tissue at YNHH or from Tolland County residents.
Zheng and colleagues have also examined the levels of the chemical compounds DDT, DDE, hexachlorobenzene (HCB) or benzene hexachloride (BHC), oxychlordane and trans-nonachlor in the breast adipose tissue of women with and without breast cancer. No significant difference was found in the levels of these compounds between breast cancer cases and their matched controls.
Other Yale Cancer Center members collaborating on these research projects include Theodore Holford, Ph.D., Susan T. Mayne, Ph.D., Barbara Ward, M.D., and Darryl Carter, M.D. Other investigators from the Yale University School of Medicine, including Patricia Owens and Robert Dubrow, M.D, Ph.D., also participated in the study.
The Yale Cancer Center is one of a select network of comprehensive cancer centers in the country designated by the National Cancer Institute and the only one in Southern New England. Bringing together the resources of Yale-New Haven Hospital and the Yale University School of Medicine, its mission encompasses patient care, research, cancer prevention and control, community outreach and education. The Cancer Information Service, a Yale Cancer Center program funded by the National Cancer Institute, provides up-to-date information on cancer prevention, detection and treatment. Trained cancer information specialists are available to answer questions Monday through Friday from 9:00 a.m. to 4:00 p.m. at 1-800-4-CANCER (1-800-422-6237).