A study in postmenopausal women in the French E3N prospective cohort indicated bisphosphonate use was not associated with a reduced risk of breast cancer. These findings were reported by Fournier et al in the Journal of Clinical Oncology.
The study included 64,438 postmenopausal women. Data were from biennial questionnaires matched with data from a drug reimbursement database. Patients were followed for an average of 7.2 years, from 2004 to 2011.
Risk of Breast Cancer
A total of 2,407 first primary breast cancers were identified. The hazard ratio for breast cancer associated with exposure to bisphosphonates was 0.98 (95% confidence interval = 0.85–1.12). A reduction in breast cancer risk (hazard ratio = 0.56, 95% CI = 0.36–0.87) was confined to the year after the start of bisphosphonate treatment, with the finding likely reflecting a healthy screenee bias.
No significant modification of the effect of bisphosphonate use was found for age; body mass index; time since menopause; or use of hormone replacement therapy, calcium supplements, or vitamin D supplements. No heterogeneity of effect was observed across different bisphosphonates, and no trends were observed according to cumulative bisphosphonate dose, duration of use, or time since last use. No variation in hazard ratios was observed across breast cancers, according to estrogen receptor or invasive or in situ status.
The investigators concluded: “In our observational cohort of postmenopausal women observed from 2004 to 2011, [bisphosphonate] use, likely prescribed for the management of osteoporosis, was not associated with decreased breast cancer incidence.”
The study was supported by the French National Cancer Institute and Cancéropôle Ile-de-France.
Marie-Christine Boutron-Ruault, MD, PhD, of Inserm, Université Paris-Sud, is the corresponding author of the Journal of Clinical Oncology article.
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