Osteoporosis drug may shield bones from breast cancer

Women with early stage breast cancer who had taken oral bisphosphonates, either before or after diagnosis of their cancer, had a reduced risk of bone metastasis, a news study shows. (Credit: iStockphoto)

A common treatment for osteoporosis appears to improve survival rates for women with breast cancer by slowing bone metastasis.

“Skeletal metastases develop in up to 70 percent of women who die from breast cancer,” says Richard Kremer, a professor in the Faculty of Medicine at McGill University and co-lead author of the study. “This causes considerable suffering and is life-threatening. Preventing this could translate into saving a significant number of lives.”

Kremer and co-lead author Nancy Mayo worked with colleagues to evaluate data from more than 21,000 women diagnosed with breast cancer.

The relationship between use of oral bisphosphonates, a common osteoporosis medication, and development of bone metastases after diagnosis with breast cancer was evaluated in two groups of women: those with early stage, localized, cancer and those whose cancer had spread to lymph nodes.

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Women with early stage breast cancer who had taken oral bisphosphonates, either before or after diagnosis of their cancer, had a reduced risk of bone metastasis, their findings show. In addition, women with later stage cancer, who took oral bisphosphonates post-diagnosis, also had a significantly reduced risk of bone metastasis.

The researchers also established a dose-response relationship with oral bisphophonate use in women with local disease: longer time spent on bisphophonate medication resulted in a greater reduction of bone metastases.

Their findings are reported in the Journal of the National Cancer Institute.

“Our study is novel in that it mainly involved women who were post-menopausal and in whom bone-turnover is high due to osteoporosis,” says Kremer. “We believe that this process results in an environment that is favorable for tumor cell growth and consequent metastasis.

“We know that bisphosphonates work by slowing down this bone-turnover. This will, in turn, make it harder for tumor cells to establish in the bone and may explain why we saw such a decline in metastasis.”

Mayo says the association between the medication and improved survival merits further investigation. “Ours was an epidemiological study, involving a large number of women strengthening the importance of the findings.

“However, clinical interventional studies are needed before the results can be translated into standard clinical practice and guidelines.”

The Canadian Institutes of Health Research, the Canadian Breast Cancer Research Initiative, the Quebec Network for Research on Drug Use, the Fonds de recherche du Québec–Santé, and the Susan G. Komen Foundation supported the work.

Source: McGill University