A recent population-based, case-control study conducted from 2003 to 2006 has reported a reduced risk of breast cancer among women using bisphosphonates : 2936 incident cases of invasive breast cancer identified in the Wisconsin cancer registry and 2975 controls identified from drivers’ license lists were interviewed. Multivariate methods were used to control for confounding by age, obstetric history, family history, menopausal status, age at menopause, hormone use, mammography, osteoporosis, smoking, and ‘height change’. Participation rates for cases and controls were 74% and 67%, respectively. Among women who used bisphosphonates within the preceding year (current use), the odds ratio (OR) for bisphosphonate users was 0.67 (95% confidence interval 0.51–0.89); among women who last used bisphosphonates more than a year previously, the OR was 0.91 (95% confidence interval 0.50–1.64). For durations of use of 3–12, 13–24, and ≥ 25 months, the ORs were 0.78, 0.69 and 0.63, respectively (trend [i]p[/i] = 0.01). The risk reduction was limited to women who were not obese (body mass index < 30 kg/m[+]2[/+]); among obese women, the risk was increased, but not significantly.
The investigators concluded that their ‘confidence in these results [was] strengthened by the large size of the study, the population-based sampling, and … consideration of important confounders’.
Department of Public Health and Family Medicine, University of Cape Town, South Africa
Newcomb PA, Tretham-Dietz, Hampton JM. Bisphosphonates for osteoporosis treatment are associated with reduced breast cancer risk. Br J Cancer 2010;102:799-802. Published March 2, 2010.
Shapiro S. Commentary: Bias in the evaluation of low-magnitude associations: an empirical perspective. Am J Epidemiol 2000;151:939-45.