Drugs commonly prescribed to prevent bone thinning probably help prevent the spread of early breast cancer to the bones in a few women, when taken in addition to standard cancer therapies. However, the overall benefits may be small, for example preventing spread to bone or death in about one extra woman in every 100 treated for about five years. This is a complex area because many of the treatments for breast cancer are known to worsen bone thinning, but there are other bone strengthening benefits to these drugs.
This large review of 44 studies with more than 37,000 participants looked at women with either early breast cancer or advanced breast cancer with or without bone involvement.
The reviewers also concluded that for women with cancer that had already spread to the bones, bisphosphonates reduced their chance of getting a fracture or bone pain.
Denosumab worked better than bisphosphonates for these women. For women with advanced breast cancer without bone involvement, drugs to prevent bone-thinning seemed to make no difference.
The study suggests more women with breast cancer might benefit from bisphosphonates or denosumab but implies that a discussion about the likely risks and benefits of treatment would also be worthwhile.
Why was this study needed?
Breast cancer is one of the commonest cancers in the UK, with more than 55,000 new cases each year. If breast cancer spreads, it often spreads to the bones. This is known as bone metastases. Bisphosphonates, drugs that affect bone growth, are sometimes used to try to prevent bone metastases. Bisphosphonates and a newer drug called denosumab are also used to treat people with bone metastases from breast cancer.
There are many studies of how bone-modifying drugs work for women with different types of breast cancer. This study is the fourth update of the topic by the Cochrane collaboration and includes 10 new studies.
What did this study do?
Researchers carried out a systematic review, with meta-analyses of results for women with early, advanced, and breast cancer that had spread to the bones.
They searched for all randomised controlled trials comparing drugs that affected bone growth with each other, or with a placebo.
For early or advanced breast cancer, they looked to see if drugs prevented bone metastases. They found 17 studies with 26,129 participants with early breast cancer and three studies with 330 participants with advanced breast cancer.
For cancer that had spread to the bone, they looked to see if drugs prevented fractures or bone pain. Researchers pooled the results in meta-analyses. They found 24 studies with 10,853 participants with breast cancer that had spread to the bone.
The quality of evidence for the main outcomes reviewed was moderate to high so that we can be fairly confident in the estimates of these effects.
What did it find?
- For women with early breast cancer, bisphosphonates lowered the chances of cancer spreading to the bone by 14% (relative risk [RR] 0.86, 95% confidence interval [CI] 0.75 to 0.99, based on 11 studies with 15,005 women). The absolute risk was 9% for women who didn’t take a bisphosphonate, compared with 7.7% for women who did take a bisphosphonate, meaning just over one person on average in every 100 would benefit.
- For women with early breast cancer, bisphosphonates improved overall survival in studies with up to 10 years follow up by 8% (hazard ratio 0.91, 95% CI 0.83 to 0.99, based on 9 studies with 13,949 women). The absolute risk was 8% for women who didn’t take a bisphosphonate, compared with 7.3% for women who did take a bisphosphonate, meaning just under one person, on average, in every 100 would benefit.
- For women with advanced breast cancer which had not spread to the bone, bisphosphonates did not seem to lower the chances of cancer spreading to the bone (RR 0.96, 95% CI 0.65 to 1.43, based on three studies with 330 women)
- For women with breast cancer which had spread to the bone, bisphosphonates lowered the chances of a fracture or bone pain by 14% (RR 0.86, 95% CI 0.78 to 0.95, based on 9 studies with 2810 women).
- For women with breast cancer that had spread to the bone, denosumab lowered the chances of a fracture or bone pain by 22% compared to a bisphosphonate (RR 0.78, 95% CI 0.72 to 0.85, based on three studies with 2,345 women).
What does current guidance say on this issue?
NICE published an evidence summary on the use of bisphosphonates to prevent recurrence of breast cancer and improve survival in July 2017. It does not make specific recommendations for the use of bisphosphonates, but says: “Local decision makers need to take safety, efficacy, cost and patient factors into account when considering the likely place in therapy of adjuvant bisphosphonates.”
NICE’s 2012 technology appraisal of denosumab says: “Denosumab is recommended as an option for preventing skeletal-related events (pathological fracture, radiation to bone, spinal cord compression or surgery to bone) in adults with bone metastases from breast cancer … if bisphosphonates would otherwise be prescribed and the manufacturer provides denosumab with the discount agreed in the patient access scheme.”
What are the implications?
The results add further evidence to support previous conclusions about the potential role of drugs that affect bone growth in the treatment of women with breast cancer.
It updates the evidence for adding bisphosphonates to the treatment of women with early breast cancer, but absolute reductions in risk are small and will require individual discussions with women considering the frequency of side effects from these medications and with their breast cancer treatment. These were not quantified here.
Citation and Funding
O’Carrigan B, Wong MHF, Willson ML, et al. Bisphosphonates and other bone agents for breast cancer. Cochrane Database Syst Rev. 2017;(10):CD003474.
No funding information was provided for this study.
NICE. Denosumab for the prevention of skeletal-related events in adults with bone metastases from solid tumours. TA 265. London: National Institute for Health and Care Excellence; 2012.
NICE. Early breast cancer (preventing recurrence and improving survival): adjuvant bisphosphonates. ES 15. London: National Institute for Health and Care Excellence; 2017.
Jin A, Cobb J, Hansen U, et al. The effect of long-term bisphosphonate therapy on trabecular bone strength and microcrack density. Bone Joint Res. 2017;6(10):602-9.
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