Postmenopausal women who take estrogen as a hormone replacement therapy do not have an increased risk of developing breast cancer, according to a study that is part of the NIH-funded Women's Health Initiative and was published in the April 12 issue of the Journal of the American Medical Association, the Wall Street Journal reports (Parker-Pope, Wall Street Journal, 4/12). Marcia Stefanick, a professor of medicine at Stanford University, and colleagues analyzed data from a previous WHI study on estrogen-only HRT to examine women's risk of breast cancer (Shelton, Orlando Sentinel, 4/12). For the original study -- which was conducted from 1993 to 1998 and published in the Feb. 13 issue of the Archives of Internal Medicine -- researchers randomly assigned 10,739 women ages 50 to 79 who had hysterectomies to take either Wyeth's estrogen pill Premarin or a placebo. Women with intact uteruses are not given estrogen alone because it increases the risk of developing uterine cancer (Kaiser Daily Women's Health Policy Report, 2/14). All cases of breast cancer diagnosed among the participants through Feb. 29, 2004, were included in the current study (Stefanick et al., Journal of the American Medical Association, 4/12). The current study was scheduled to last until 2005 but was halted by NIH in February 2004, citing a study finding that women who took Premarin had a slightly increased risk of stroke compared with women who were taking a placebo (Wall Street Journal, 4/12).

Results
Researchers found a total of 104 breast cancer cases among women who took Premarin and 133 breast cancer cases among women who took the placebo (BBC News, 4/11). Researchers said the difference in breast cancer incidence between the two groups is not statistically significant. However, when researchers excluded women who had stopped taking their pills -- about 54% of the participants -- they found that women who took Premarin had a statistically significant lower risk (33%) of developing breast cancer than women who were taking the placebo (Peres, Chicago Tribune, 4/12). However, the study also finds that women who took Premarin had about 50% more mammograms that required follow-up visits and 33% more biopsies than women in the group taking the placebo (Ubelacker, CP/Globe and Mail, 4/12). According to the Journal, there were several "quirks" in the WHI study, including that nearly half of the trial participants were obese -- fat is a source of estrogen and could "blunt" the effects of estrogen pills -- and about 41% of the participants had their ovaries removed, which has been shown possibly to lower the risk of developing breast cancer (Wall Street Journal, 4/12). Stefanick and colleagues concluded, "Initiation of [estrogen-only HRT] in women after hysterectomy should continue to be based on careful consideration of potential risk and benefits for a given individual" (Reuters Health, 4/11).

Media Coverage
Several broadcast programs reported on the study:

• ABCNews' "World News Tonight": The segment includes comments from Stefanick; June LaValleur, a physician at the University of Minnesota; and a study participant (Stark, "World News Tonight," ABCNews, 4/11). The complete segment is available online.
  


• NBC's "Nightly News": Robert Bazell, NBC chief science and health correspondent, discusses the study (Bazell, "Nightly News," NBC, 4/11). The complete segment is available online in Windows Media. A Weblog entry by Bazell about the study is available online.
  


• NPR's "All Things Considered": The segment includes comments from JoAnn Manson, professor of medicine at Harvard Medical School; Janet Pregler, director of the Iris Cantor Women's Health Center at the University of California-Los Angeles; Joseph Sanfilippo, president of the American Society of Reproductive Medicine; Stefanick; and Hugh Taylor, professor of obstetrics and gynecology at Yale University and a paid speaker for a hormone manufacturer (Aubrey, "All Things Considered," NPR, 4/11). The complete transcript and expanded NPR coverage is available online. The complete segment is available online in RealPlayer.