The observed increase in breast cancer incidence in the Women's Health Initiative was clinically insignificant and should be weighed against other mortality benefits.

“the absolute risk increase was 0.1 percent it was a difference of one case per thousand”

The increased breast cancer risk observed in the Women's Health Initiative is largely attributed to the combination of estrogen and medroxyprogesterone acetate, while estrogen-only therapy did not sho

“the increased risk of breast cancer seen with estrogen plus progestin was mostly be attributable if not entirely attributable to the progesterone to the medroxy progesterone acetate”