HRT link to breast cancer study questioned

The UK Million Women Study (MWS), the largest study of postmenopausal women and HRT, produced four reports (2003, 2004, 2006 and 2011) and is credited with confirming findings in the Women’s Health Initiative (WHI) that women currently using HRT are more likely to develop breast cancer than those who are not using HRT.
While the MWS has been lauded for its scale and size, a review by Australian endocrinologist Professor Henry Burger and colleagues argues the observational study is flawed and its findings do not adequately satisfy the principles of causation.
“In terms of time order, information bias, detection bias, confounding, statistical stability and strength of association, dose/duration response, internal consistency, external consistency and biological plausibility the study was defective,” they wrote.
They propose that had detection bias resulted in the identification in women aged 50–55 years