Benzodiazepines and risk for breast cancer

The study aim is to evaluate benzodiazepine use and risk for breast cancer in Ontario, Canada, by using a population-based case-control study design.

Cases were a random sample of women aged 25 to 74 years identified through the Ontario Cancer Registry and diagnosed with breast cancer between 1996 and 1998 (n = 3133). Controls were an age-matched random sample of women (n = 3062). Cases and controls completed a self-administered questionnaire that included questions about their past use of benzodiazepines (defined as daily use for at least 2 months) and potential confounders. Individual classes of benzodiazepines also were evaluated. Multivariate logistic regression analysis was conducted, and odds ratios (ORs) and 95% confidence intervals (CIs) were estimated.

Compared with nonusers, ever use of benzodiazepines was not significantly associated with risk for breast cancer (OR, 1.06; 95% CI, 0.88-1.27). No apparent trends were observed for duration of use, time since first use, or time since last use. Estimates according to individual classes of benzodiazepines, including diazepam, lorazepam, and chlordiazepoxide, also were not statistically significant.

Our data show no association between benzodiazepine use and breast cancer risk. Results confirm findings from previous studies that diazepam use does not increase the risk for breast cancer and also suggest no association with the use of other benzodiazepine compounds.