In the WHI, 16,608 postmenopausal women American, 50 to 79 years of age, who had not under gone hysterectomy were randomly Assigned to receive conjugated equine estrogens combined Either 0.625 mg / day plus medroxyprogesterone acetate 2.5 mg / day, or placebo.

After the original trial completion date, was presented reconstructive tools for continued follow-up for breast cancer incidence, and was obtained from 12 788 (83%) of the surviving participant, the report authors, led by Rowan T. Chlebowski, MD, PhD, from the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center in Torrance, California.

The WHI authors ormed intention-to-treat analysis and found That combined estrogen-progestin hormone therapy plus Increased the incidence of invasive breast cancer, compared with placebo (385 cases [0.42% per year] vs. 293 cases [0.34% per year] ).

That They Also found significantly more women in the combined hormone therapy group had positive lymph nodes with breast cancer than in the placebo group (81 [23.7%] vs 43 [16.2%]).

The authors point out That this finding conflicts with observational studies. With some exceptions, observational studies, "have combined hormone therapy use associated with an Increase in Breast Cancers That Have Favorable Characteristics" and are at a lower stage than breast cancers in women not Receive the therapy, the study authors write.

Observational studies have found That Also women with breast cancer combined hormone therapy survived longer Receiving Than Those not Receiving therapy. This was not the case with the WHI's latest data, the authors report.

In the WHI data, there were more deaths directly Attributed to breast cancer among the hormone group than among the placebo group (25 deaths [per year 0.03%] deaths vs 12 [0.01% per year], hazard ratio 1.96, 95% confidence interval, 1.00 - 4.04, P = .049).

These deaths represent 2.6 and 1.3 deaths per 10,000 women per year, respectively, the authors write.