Could bisphosphonates reduce risk of bone metastasis in breast cancer?

According to a recent study, low-dose oral bisphosphonates administered to prevent or treat postmenopausal osteoporosis may be associated with a lower risk of skeletal metastasis in patients with early- or more advanced-stage breast cancer.

The findings are based on analysis of health administrative data from a historical cohort of 21,664 women diagnosed with breast cancer in Quebec, Canada. Researchers from McGill University Health Centre stratified the cohort according to disease stage (0-II or III) at time of diagnosis. The primary outcome was time to development of bone metastasis. Exposure was considered bisphosphonate use prediagnosis, postdiagnosis, both, or neither, and a cumulative index of drug exposure.

In women with local disease at diagnosis, use of bisphosphonates only postdiagnosis or continuing on them after breast cancer diagnosis was associated with a decline in risk of bone metastasis from 45% to 28%. The reduction in risk associated with bisphosphonates was nearly 50% in women with regional disease who used the drugs postdiagnosis, regardless of whether they had used bisphosphonates prediagnosis.

Researchers also observed a statistically significant dose-response trend that related increased use with lower risk (slope = 0.94, 95% confidence interval = 0.90 to 0.99). Also, bisphosphonates were associated with a decreased risk of all-cause mortality similar to that for development of bone metastasis.

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Investigators concluded that low-dose bisphosphonates used for the prevention or treatment of postmenopausal osteoporosis were tied to lower risk of skeletal metastasis in patients with early- and advanced-stage breast cancer.

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