Breast cancer risk hazy in hormone study

Lebanese researchers studied data from the Women’s Health Initiative (WHI) clinical trial of oestrogen and progestin therapy and found its effect on breast cancer risk was strongest in women whose pre-treatment levels of total oestradiol, bioavailable oestradiol, and oestrone were in the lowest quartiles.

Risk was more than doubled for women in the lowest quartile of endogenous oestradiol, relative to placebo. Women in the highest quartile of total oestradiol had a slightly decreased risk.