MONDAY, May 8, 2006 (HealthDay News) -- Postmenopausal women who've had a hysterectomy and have used estrogen therapy for 15 years or more appear to be at higher risk of breast cancer, a new study found.
The new findings helped to clarify researchers' understanding of the potential link between estrogen therapy and breast cancer. Past studies that looked at estrogen taken with the hormone progestin have linked this combination to an increased risk of breast cancer among postmenopausal women. But results released in April from the Women's Health Initiative, a large clinical trial of hormone therapy, found no significant connection between estrogen therapy alone and breast cancer in women who took the hormone for seven years.
"Estrogen only causes cancer after prolonged exposure," said Dr. Wendy Y. Chen, lead researcher of the new study, who's with Brigham and Women's Hospital and Dana Farber Cancer Institute, in Boston.
Chen's team believes the effect of estrogen is cumulative. "We found that there was a 42 percent increased risk for all types of breast cancer for women who had used estrogen alone for 20 or more years," she said. However, for the type of breast cancer that is hormone sensitive, there was a 48 percent increased risk after 15 years of estrogen use, she said.
The study findings appear in the May 8 issue of the Archives of Internal Medicine.
For the study, Chen and her colleagues collected data on 28,835 women who were part of the Nurses' Health Study. During the study period, 934 women developed invasive breast cancer. These included 226 women who had never used hormones, typically to ease menopausal symptoms such as hot flashes, vaginal dryness and loss of energy, and 708 women who were using estrogen at the time.
Given these findings, women need to consider whether they want to use estrogen over an extended period, Chen said. "For women who use estrogen alone, and have been on it for more than 10 years, they would want to consider how much longer they want to remain on estrogen," she said.
"If you are taking it for less than 15 years, we haven't seen a significant increase in risk," Chen added. "But after 15 years, women should speak to their physician about the benefits of being on estrogen and how would that be weighted against the risks."
Women who decide to stay on estrogen need to have regular mammograms, Chen said.
Dr. Jennifer Wu, an obstetrician/gynecologist at Lenox Hill Hospital in New York City, thinks these findings show that the current guidelines for estrogen use make sense.
"This study highlights the importance of appropriate use of hormone therapy," Wu said. "Patients must understand that the benefits of estrogen come with certain risks."
"Current guidelines for estrogen therapy hold true," Wu said. "The current recommendation for estrogen therapy is to use the lowest effective dose for the shortest duration of time."
More information
The Women's Health Initiative can tell you more about estrogen therapy.
