LOS ANGELES, July 1 (Xinhua) — A new study led by scientists at the U.S. National Institutes of Health (NIH) has found that two common forms of hormone therapy may alter breast cancer risk in women under the age of 55.
According to the study, women who received unopposed estrogen hormone therapy (E-HT) had a lower risk of developing breast cancer compared to those who did not use hormone therapy. In contrast, women treated with combined estrogen plus progestin hormone therapy (EP-HT) were found to have a higher risk of developing the disease.
The findings, published Monday in The Lancet Oncology, are based on an extensive analysis of data from over 459,000 women under the age of 55 across North America, Europe, Asia and Australia.
“Our study provides greater understanding of the risks associated with different types of hormone therapy, which we hope will help patients and their doctors develop more informed treatment plans,” said lead author Katie O’Brien, a researcher at NIH’s National Institute of Environmental Health Sciences (NIEHS).
The study found that E-HT use was associated with a 14 percent reduction in breast cancer incidence compared to non-users. The protective effect was more pronounced among women who began E-HT at a younger age or used it for a longer duration.
Conversely, women using EP-HT experienced a 10 percent higher risk of breast cancer, which increased to 18 percent among those who used the therapy for more than two years.
The cumulative risk of breast cancer before age 55 was estimated at 3.6 percent for E-HT users, 4.5 percent for EP-HT users, and 4.1 percent for women who never used hormone therapy, according to the study.
The researchers also noted that the elevated risk associated with EP-HT was particularly significant among women who had not undergone hysterectomy or oophorectomy, emphasizing the importance of considering surgical history when evaluating hormone therapy options.
“These findings underscore the need for personalized medical advice when considering hormone therapy,” said NIEHS scientist and senior author Dale Sandler. ■