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UW Study Links Cadmium Exposure to Breast Cancer
January 20, 2006
MADISON – Researchers at the University of Wisconsin Comprehensive Cancer Center (UWCCC) report a newly discovered link between high levels of cadmium in the body and the risk of breast cancer.
Stressing that the research team’s findings do not prove that cadmium causes breast cancer, lead author Jane McElroy, PhD, says that women in the top 25 percent of cadmium levels had twice the breast-cancer risk of women in the lowest 25 percent for cadmium levels.
The findings are published in the June 21, 2006 edition of the Journal of the National Cancer Institute.
Cadmium, which is present in both food and tobacco, is a toxic metal that accumulates in the body and is classified by the Environmental Protection Agency as a probable human carcinogen. For women who are not exposed to cadmium through their work and who do not smoke, food is the largest source of cadmium intake; for smokers, tobacco smoke is the main source of exposure. Very little cadmium is excreted, and thus the metal builds up in the body over time.
The UW study enrolled 246 women with confirmed breast cancer and 254 women without the disease; the two groups were similar in age distribution. Because urine samples indicate lifetime cadmium exposure, samples were taken from women in both groups. All participants were interviewed about known risk factors for breast cancer, including physical activity, reproductive history, alcohol consumption, height and weight, use of oral contraceptives, smoking, and other factors.
The women were then grouped according to the level of accumulated cadmium in the body. After controlling for 12 known risk factors for breast cancer, the research team found that the women in the top 25 percent for cadmium exposure had slightly more than twice the risk of breast cancer than women in the lowest 25 percent.
“We find these results provocative and deserving of a closer look,” said McElroy, a researcher with the UWCCC. “One study of this kind cannot prove a causal link. But with this high an association between exposure and risk, it’s important that we understand more about it.”
The researchers note that the study does not establish whether the association of breast cancer risk with cadmium level reflects the effect of cadmium on tumor development and growth or possibly the effects of treatment or the disease itself on cadmium levels.
The study was funded by the National Institutes of Health. Other members of the research team are Martin Shafer, Amy Trentham-Dietz and John Hampton, all of the UWCCC; and Polly Newcomb of the Fred Hutchinson Cancer Research Program in Seattle. |
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