Stony Brook study finds cadmium-breast cancer link

Long Island women with breast cancer were more likely to have elevated levels of the heavy metal cadmium in their bodies, Stony Brook researchers have found - bolstering evidence from prior research that also linked the malignancy to the toxin.

The study, published online this past week, while not establishing a cause-effect relationship, adds to a growing body of similar evidence from elsewhere in the country and the world.

Dr. John Kovach, a professor of preventive medicine, said the high incidence of breast cancer on Long Island cannot be fully explained by traditional risk factors - genetics, smoking and obesity. So he's searching the environment for clues.

"I have been interested in cadmium for a long time as a potential environmental toxin," said Kovach, lead author of the investigation published in the Open-Access Journal on Aging.

Kovach and colleagues gathered urine samples from 100 Long Island women who had breast cancer and 98 women who never had the disease.

Correlation found

All 100 women who had breast cancer were post-menopausal and also had elevated levels of cadmium in their urine. The 98 women who never had breast cancer were younger, pre-menopausal and had barely perceptible levels of the heavy metal when tested, the study found.

When weighing that evidence, Kovach concluded that not only does cadmium increase in the body as people age, it also escalated by 2.5 times the risk of breast cancer.

Kovach compared the data to urine samples and medical records of women participating in the National Health and Nutrition Examination Survey, an ongoing project of the National Institutes of Health. Participants in the national study also showed a correlation between breast cancer and the highest urinary cadmium levels, Kovach said.

The national incidence of breast cancer is 122.9 per 100,000 women, but on Long Island it is 142.7 per 100,000, according to the National Institutes of Health data used in the Long Island Breast Cancer study.

Neither the Long Island women nor those in the national investigation had occupational exposures to cadmium. Precisely how much of a role the heavy metal plays in breast cancer will be the subject of future research, Kovach said.

Shellfish, namely oysters and clams, contain significant concentrations of the metal, he said. Trace amounts are also found in some potatoes and other root vegetables, such as beets, he said.

Cadmium has been linked to cancer before. A 2006 Wisconsin study linked the metal to breast cancer, and studies in Europe suggest associations between cadmium and both breast and prostate cancers.

The toxin accumulates in the body, Kovach said, which means older women tend to have higher levels.

Still, finding a correlation between cadmium and breast cancer does not suggest cause and effect, experts say. In fact, the American Cancer Society earlier this year lashed out against the Presidential Cancer Panel when it issued a report suggesting a range of environmental toxins, including cadmium, as playing a role in numerous forms of cancer. Cancer society officials said researchers should devote their resources to investigating more widely accepted risk factors.

Evidence of risk

During a meeting in Manhattan last week, sponsored by the National Institute on Environmental Health Sciences and the National Cancer Institute, researchers said the Stony Brook study is important because it provides evidence that cadmium somehow increases breast cancer risk.

"It's certainly something that warrants more investigation because this is the second [U.S.] study to show a presence of urinary cadmium and a risk for breast cancer," said Dr. Susan Pinney, an epidemiologist at the University of Cincinnati.

Scientists at the meeting discussed a range of heavy metal toxins, including cadmium, as possible breast cancer culprits.

On Long Island, Dr. Francis Arena, a Great Neck breast cancer specialist, said it's important to investigate all possible causes of the disease.

"This type of research is key because there are so many missing pieces in the causes of breast cancer," said Arena, co-author of a new book on the history of breast cancer as viewed through art and sculpture. "Obviously, there is a genetic component," Arena said, "but clearly there is something else that happens in the vast majority of patients that is unexplained."