Effect of bisphosphonate use on risk of postmenopausal breast cancer: Results from the randomized clinical trials of alendronate and zoledronic acid
Menée à partir des données de deux essais évaluant respectivement l'alendronate et l'acide zolédronique et incluant respectivement 6 459 femmes âgées de 55 à 81 ans (durée moyenne de suivi : 3,8 ans) et 7 765 femmes âgées de 65 à 89 ans (durée moyenne de suivi : 2,8 ans), cette étude évalue l'effet de l'utilisation de bisphosphonates sur le risque de cancer du sein après la ménopause
Importance : Studies have shown that bisphosphonates may have antitumor and antimetastatic properties. Recently, observational studies have suggested a possible protective effect of bisphosphonates on breast cancer, but the effect of bisphosphonate use on risk of breast cancer has not been tested in randomized trials. Objective : To assess the relationship of postmenopausal breast cancer incidence and bisphosphonate use using data from 2 randomized (1:1), double-blind, placebo-controlled trials. Design, Setting, and Participants : The Fracture Intervention Trial (FIT) randomly assigned 6459 women aged 55 to 81 years to alendronate or placebo for a mean follow-up of 3.8 years. The Health Outcomes and Reduced Incidence With Zoledronic Acid Once Yearly–Pivotal Fracture Trial (HORIZON-PFT) randomly assigned 7765 women aged 65 to 89 years to annual intravenous zoledronic acid or placebo for a mean follow-up of 2.8 years. Data were collected at clinical centers in the United States (FIT and HORIZON-PFT) and in Asia and the Pacific, Europe, North America, and South America (HORIZON-PFT). Women, in either study, with recurrent breast cancer or who reported a history of breast cancer were excluded from analyses. In each trial, a blinded review was conducted of each cancer adverse event report to verify incident invasive breast cancer cases. The primary analysis compared events in the active vs placebo group using a log-rank test. Intervention : Alendronate vs placebo (FIT) or zoledronic acid vs placebo (HORIZON-PFT). Main Outcomes and Measures : Hazard ratio for incident breast cancer in the bisphosphonate treatment group compared to the placebo group. Results : There was no significant difference in the rate of breast cancer in FIT: 1.5% (n = 46) in the placebo group and 1.8% (n = 57) in the alendronate group (hazard ratio [HR], 1.24 [95% CI, 0.84-1.83]). In HORIZON-PFT, there was also no significant difference: 0.8% (n = 29) in the placebo group and 0.9% (n = 33) in the zoledronic acid group (HR, 1.15 [95% CI, 0.70-1.89]). There was also no significant difference when the data from FIT and HORIZON-PFT were pooled (HR, 1.20 [95% CI, 0.89-1.63]). Conclusions and Relevance : These 2 randomized clinical trials do not support the findings from observational research. Contrary to the results from observational studies, we found that 3 to 4 years of bisphosphonate treatment did not decrease the risk of invasive postmenopausal breast cancer.