Using a mouse model of breast cancer metastasis, the researchers found that a calcium deficiency may increase the tendency of advanced breast cancer to target bone. Dietary calcium, they reason, might help prevent the spread of breast cancer to bone and serve as an adjuvant treatment during therapy.

Their findings are presented in the Oct. 1 issue of Cancer Research, a journal of the American Association for Cancer Research.

According to the researchers, about 70 percent of patients who develop advanced breast cancer will have secondary tumors in the bone. The spread of cancer to bones leads to cellular processes that physically break down existing bone, leading to further pain and illness. In fact, the breakdown of bone and subsequent bone re-growth forms what senior author Colin R. Dunstan, Ph.D., terms a vicious cycle that turns bone into an environment conducive to cancer growth.

To better understand the role of bone turnover in the spread of cancer, Dunstan and his team compared the effects of a low- and high-calcium diet in mice. They found that dietary calcium deficiency “ independent of the chemical factors that control turnover “ was related to a significantly higher increase in cancer cell proliferation and the total proportion of bone that had been penetrated.

These results could have implications for patients with breast cancer bone metastases or who are at high risk for developing metastatic disease, Dunstan said. Many older women in our community are known to be calcium deficient due to low calcium dietary intake or due to vitamin D deficiency. These women could be at increased risk for the devastating effects of bone metastases.

According to Dunstan, his results call for further, directed clinical trials to investigate how calcium and vitamin D status influence progression to metastatic disease, and to determine if corrections of calcium and vitamin D deficiencies are important in breast cancer patients.

The ANZAC Research Institute study was funded by the National Health and Medical Research Council of Australia and the New South Wales Government.

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