Estrogen Plus Progestin Associated with Risk of Breast Cancer
The initial results from the Women’s Health Initiative (WHI) randomized, placebo-controlled trial found that women who received the estrogen plus progestin for five years had higher rates of breast cancer and ovarian cancer than the women who received the placebo. Researchers from the Los Angeles Biomedical Research Institute analyzed and reported updated information from the WHI study on breast cancer incidence and for the first time, information on breast cancer mortality. After the original trial completion date (March 31, 2005) involving 16,608 postmenopausal women aged 50 to 79 years, re-consent was required for the 11 year follow-up for breast cancer incidence and was obtained from 12,788 (83 percent) of the surviving participants. The results were the group taking the estrogen plus progestin pill was associated with more invasive breast cancers (385 cases [0.42% per year) compared with the placebo group (293 cases [0.34% per year). There were also twice as many deaths from breast cancer in the estrogen plus progestin group in comparison to the placebo group. These longer follow-up results indicate that hormone replacement therapy increased the risk of breast cancer and increased breast cancer mortality.