Combination Hormone Replacement Therapy and Risk of Breast Cancer
An invited commentary by Drs. Paula Silverman and Cheryl Thompson
In 2002, the combination therapy arm of the Women's Health Initiative trial was stopped when the investigators concluded that the risks, including increased breast cancer risk, outweighed the benefits. Since then, there has been a strong shift in prescribing practice, with fewer women being prescribed combination therapy each year. With this changing practice, we expected the number of post-menopausal breast cancer cases to decline. Indeed, this has been the case though there has been some controversy about whether the decline was due to less HRT use or fewer women receiving mammograms, another recent trend.
This new report in BJC that attempted to address shortcomings in previous studies by utilizing the Breakthrough Generations Study, which includes more detailed data on both HRT use and timing with menopause, suggests that the change in prescribing practices may have a larger than expected impact on cancer incidence. Statistical analyses on their data suggest that not having yearly updated data on HRT and menopausal status, typical of most epidemiological studies, may have underestimated the effect by up to 59%.