Bisphosphonate use and the risk of breast cancer: a meta-analysis of observational studies

PurposeTo summarize current evidence of the association of bisphosphonate use with breast cancer risk, we used a systematic review and meta-analysis of observational studies to explore this issue. MethodsA comprehensive search was conducted on PubMed, EMBASE, and the Cochrane Library. Pooled relative risk (RR) estimates and 95% confidence intervals (CIs) were calculated using the random effects model. ResultsBisphosphonate use was associated with a 16% lower breast cancer risk (pool RR0.84, 95%CI 0.77-0.90, n=8). A protective effect of bisphosphonate was found in cohort studies (RR 0.85, 95%CI 0.80-0.90, n=4) and case-control studies (RR 0.78, 95%CI 0.64-0.96, n=4).We also found that the use of bisphosphonate resulted in a statistically significant reduction in all breast cancer risk (RR 0.87, 95%CI 0.81-0.93) and greater reduction in invasive breast cancer risk (RR 0.78, 95%CI 0.68-0.91) and contralateral breast cancer risk (RR, 0.41; 95% CI, 0.20-0.84).With respect to the type of bisphosphonate, we found that alendronate and etidronate resulted significant reduction in breast cancer risk. The short-term use of bisphosphonate (<1y) led to nonsignificant change (RR 0.93, 95%CI 0.86-1.00), but a significant 26% reduction of breast cancer risk was noted with long-term use (>1y) (RR 0.74, 95%CI 0.66-0.83). ConclusionsOur results supported bisphosphonate as being effective in preventing breast cancer, including invasive and contralateral breast cancer. Furthermore, the long-term use (>1y) of bisphosphonate was more significant in lowering breast cancer risk.