Cadmium linked to breast cancer

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Women with the highest urinary levels of cadmium have more than a two-fold increased risk of breast cancer than women with the lowest levels, according to the results of a study in the Journal of the National Cancer Institute for June 21. However, further studies are needed to determine if these elevated levels are a cause or effect of breast cancer.

Although cadmium, a heavy metal, has been classified as a probable carcinogen by the US Environmental Protection Agency, until now no human studies have investigated its link with breast cancer, lead author Dr. Jane A. McElroy, from the University of Wisconsin Comprehensive Cancer Center in Madison, told Reuters Health. The findings from "animal studies have supported an association, and cadmium has been found in breast tissue."

In the present, population-based study, urinary levels of cadmium were compared in 246 breast cancer patients and in 254 age-matched controls. The subjects were contacted by telephone to determine the presence of known breast cancer risk factors.

Women with creatinine-adjusted cadmium levels of 0.58 micrograms/g or higher were 2.29-times more likely to have breast cancer than those with levels lower than 0.26 micrograms/g. This relationship held true after accounting for established risk factors.

The absolute risk difference between high and low cadmium levels is 45 breast cancer cases per 100,000 given an overall rate of 124 per 100,000, the authors note.

Exactly how cadmium might cause breast cancer is unclear, but "there is evidence that it has estrogenic effects. It actually competes with estrogen for the alpha receptor site," Dr. McElroy said.

Dr. McElroy believes that if the current findings are replicated in a larger study and cadmium's etiologic role is clarified, it could lead to tighter restrictions on how the heavy metal is disposed of in the environment