BOSTON, May 8 (UPI) -- A study published Monday shows that estrogen therapy does raise breast-cancer risk, but only if used more than 20 years.
The Nurses' Health Study -- which focused on data from more than 120,000 registered nurses -- revealed a significant increase in breast-cancer risk among postmenopausal women who used estrogen-alone therapy for 20 or more years, but no increased risk among postmenopausal patients on estrogen-alone treatment for fewer than 10 years.
The study also showed an insignificant increase in breast-cancer risk among women who used estrogen-alone therapy for 10 to 20 years. The study appears in this week's Archives of Internal Medicine.
Lead investigator Wendy Chen, with Brigham and Women's Hospital, said the findings point to the need for women taking estrogen long term to treat or prevent osteoporosis to consider other options.
Commenting on the study results, Ginger Constantine, vice president of women's healthcare and bone repair for Wyeth Pharmaceuticals, said, "The NHS findings, in addition to recent (Women's Health Initiative) study findings on breast cancer, are very important for millions of women who are appropriate candidates for estrogen-alone therapy."
The NHS data add to a growing body of evidence suggesting that estrogen-alone therapy might not heighten breast-cancer risk if taken for shorter periods of time.
Last month doctors called "reassuring" a new analysis of data from the WHI study, which suggested that postmenopausal women who have had hysterectomies are not at greater risk for breast cancer -- if they are taking estrogen alone for a limited period.
That analysis and the NHS study data shed a more positive light on HRT, which came under scrutiny in 2002 after WHI's Estrogen plus Progestin trial showed that the combination of estrogen and progesterone had more health risks than benefits, including a higher incidence of breast cancer.
