Incidence of breast cancer in a 22-year study of women receiving estrogen-progestin replacement therapy

Abstract

Objective: To review the incidence of breast cancer in a continuous 22-year study of conjugated estrogen-medroxyprogesterone acetate hormone replacement therapy.

Methods: Eighty-four pairs of continuously hospitalized postmenopausal women who were matched for age, smoking history, and medical diagnosis were treated with estrogen-progestin hormone replacement therapy or placebo in a prospective and double-blind manner for 10 years. In the subsequent 12 years, the women were offered the choice of starting, stopping, or continuing hormone replacement therapy.

Results: After the initial 10 years, the incidence of breast cancer in the placebo group was 4.8%, whereas no cancers were found in the hormone replacement therapy group (P = .12). After an additional 12 years of follow-up, the overall incidence of breast cancer in the women who had never taken hormone replacement therapy was 11.5%, whereas no breast cancers had developed in the women who had ever taken hormone replacement therapy (P < .01).

Conclusions: These data suggest that the 22-year administration of estrogen-progestin hormone replacement therapy did not increase the incidence of breast cancer in a small group of continuously hospitalized postmenopausal women.