- A meta-analysis of 10 studies finds that bisphosphonates are associated with a 12% lower risk of breast cancer.
- 2 of the studies, both randomized controlled trials (RCTs), found no relationship but were compromised by flaws in study design.
Why this matters
- The authors call for a new RCT to resolve the discrepancy vs observational studies.
- Meta-analysis of 10 studies (n>900,000) obtained from MEDLINE, EMBASE, Cochrane libraries, ProQuest, and Web of Science.
- Study designs: 2 RCTs, 5 cohort studies, and 3 case-control studies.
- Funding: None disclosed.
- Bisphosphonate use was associated with 12% lower risk for primary breast cancer (risk reduction [RR], 0.88; 95% CI, 0.83-0.94).
- Similar associations were found with cohort (RR, 0.83; 95% CI, 0.71-0.98) and case-control studies (RR, 0.87; 95% CI, 0.80-0.95).
- 2 RCTs showed no association (RR, 1.127; 95% CI, 0.808-1.573), but were not designed to assess breast cancer outcomes (selective reporting bias).
- Stratified analysis of the 10 studies showed that longer-term bisphosphonate use (≥1 year) had a greater effect on breast cancer risk reduction (RR, 0.75; 95% CI, 0.66-0.84) than short-term use (
- Heterogeneity across studies, including differences in bisphosphonate type.
- Potential residual confounding.