(HealthDay News) – Long-term use of estrogen hormone therapy (estrogen only [ET] or estrogen plus progesterone [E+P]) is associated with a higher risk for breast cancer, according to a study presented at the annual meeting of the American Association for Cancer Research, held from March 31–April 4 in Chicago.
Wendy Y. Chen, MD, MPH, from the Dana-Farber Cancer Institute in Boston, and colleagues analyzed data for postmenopausal women from the Nurses’ Health Study, collected from 1980–2008 for those aged 30–55 years old in 1976.
During 1.57 million person-years of follow-up, the researchers found that breast cancer risk increased with duration of current E+P use without evidence for a plateau (relative risk [RR], 1.88 for 10–14.9 years; RR, 2.35 for 15–19.9 years). Long-term current ET use also correlated with increased risk (RR, 1.22 for 10–14.9 years; RR, 1.43 for 15–19.9 years). When the population was restricted to the same entry criteria as the Women’s Health Initiative trial there was still an increased risk for long-term current users (RR, 1.30 for 15–19.9 years). There was no increase in the risk of fatal breast cancer with either E+P or ET use (RR, 1.05 [95% CI, 0.67–1.68] and 1.08 [95% CI, 0.80–1.46], respectively, for 10–19.9 years of current use).
“Even though we saw an increased risk in developing breast cancer, we did not see an increased risk for dying from breast cancer,” Chen said in a statement.