Postmenopausal women carried an increased risk of advanced breast cancers following the use of estrogen plus progestin, a recent study has revealed.
As part of the study, a total of 16,608 postmenopausal women ages 50 to 79 years with no prior hysterectomy from 40 U.S. clinical centers were randomly assigned to receive combined conjugated equine estrogens, 0.625 mg/d, plus medroxyprogesterone acetate, 2.5 mg/d, or placebo pill.
After the original trial completion date re-consent was required for continued follow-up for breast cancer incidence and was obtained from 12,788 of the surviving participants.
The researchers found that in intention-to-treat analyses including all randomized participants and censoring those not consenting to additional follow-up, estrogen plus progestin compared with placebo increased the incidence of invasive breast cancer.
A significantly larger fraction of women in the combined hormone therapy group had breast cancers with positive lymph nodes compared with women in the placebo group.
"More women died of breast cancer in the combined hormone therapy group compared with the placebo group (25 deaths [0.03 percent per year] vs. 12 deaths [0.01 percent per year]), representing 2.6 vs. 1.3 deaths per 10,000 women per year, respectively," the authors write.
The study was published in the October 20 issue of JAMA.