Statins and postmenopausal breast cancer risk; results from the KARMA cohort.

[PURPOSE] To study the incidence and subtype of breast cancer in relation to incident and prevalent statin use in a contemporary Swedish prospective cohort, The Karolinska Mammography Project for Risk Prediction of Breast Cancer, KARMA.

[METHODS] A total of 35,315 postmenopausal women attending mammography and included in the KARMA cohort (Jan 2011-March 2013) with data on statin use and potential confounders were studied. During eight years of follow-up, 785 incident invasive breast cancer cases were identified.

[RESULTS] A total of 16% of women were prevalent statin users (prior to study inclusion) and 9% were incident statin users (following study inclusion). In multivariable Cox regression analyses, there was no significant association between incident or prevalent statin use and risk of incident breast cancer (HR 1.24, 95% CI 0.89-1.72, and HR 0.90, 95% CI 0.73-1.11, respectively). Similarly, no significant association was found for incident or prevalent statin use and subtype-specific risk of breast cancer.

[CONCLUSION] This prospective population-based study performed in a modern screening population with a substantial number of statin users, concurs with previous publications showing no evidence of an association between statin use and risk of postmenopausal breast cancer.