Bisphosphonates fail to prevent breast cancer in postmenopausal women

  • Rouach V & al.
  • J Bone Oncol
  • 01/06/2019

  • Miriam Davis, PhD
  • Univadis Clinical Summaries
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Takeaway

  • A large Israeli observational study of osteoporotic or osteopenic postmenopausal women fails to show that exposure to bisphosphonates protects against breast cancer onset.

Why this matters

  • This observational study using 5 levels of exposure does not support 2 prior observational studies, but does support the negative results of prior randomized controlled trials.
  • The evidence suggests that positive studies might reflect low estrogen rather than an antitumor effect of bisphosphonates.

Study design

  • Historical prospective study (n=11,717) using databases of the Israeli Maccabi Healthcare Services (MHS).
  • Exposure to bisphosphonates (alendronate or risedronate) among postmenopausal women with osteoporosis of osteopenia was stratified into quintiles of proportion of days covered (PDC) with bisphosphonates during the follow-up, which was a minimum of 5 years.
  • Breast cancer incidence was obtained from the Israel National Tumor Registry.
  • Funding: None.

Key results

  • 173 incident breast cancers were seen over a total of 130,252 person-years of follow-up.
  • Compared with PDC of 20% or lower (the lowest quintile of exposure), the adjusted HRs for breast cancer at higher quintiles were:
    • PDC 21%-40%: HR, 0.816; P=.455.
    • PDC 41%-60%: HR, 0.818; P=.420.
    • PDC 61%-80%: HR, 0.727; P=.179.
    • PDC 81%-100%: HR, 1.146; P=.504.

Limitation

  • Multiple comparisons.