Oestrogen and breast cancer: Results from the WHI trial

摘要

In The Lancet Oncology, the Women's Health Initiative (WHI) investigators report that receipt of conjugated equine oestrogen for a median of 5.9 years reduced the risk of invasive breast cancer by 23% compared with placebo (151 cases in 5310 women who received oestrogen vs 199 cases in 5429 controls; p=0.02). Women who did develop breast cancer after receipt of oestrogen had significantly reduced breast cancer-specific mortality (six deaths in the oestrogen group vs 16 deaths in controls; p=0.03) and all-cause mortality (30 deaths vs 50 deaths; p=0.04). This preventive effect occurred at all ages and continued beyond the period of oestrogen use, a carryover effect also noted in prevention trials of tamoxifen.