Adding continuous progestin to estrogen has been shown to lower the risk of endometrial cancer in postmenopausal women according to a study published December 14 in the JNCI: Journal of the National Cancer Institute.
The addition of progestin to an estrogen regimen has been known to lower the risk of endometrial cancers which are associated with estrogen alone use but just how much the addition of progestin lowers the risk of getting the disease has remained unclear.
In order to determine the effects that continuous estrogen plus progestin use has on the risk of endometrial cancer, Rowan T. Chlebowski, M.D., Ph.D., Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, and colleagues reviewed data from a randomized clinical trial by the Women's Health Initiative (WHI) that assessed 16,608 postmenopausal women aged 50-79 with intact uteri. All participants were required to have a normal endometrial biopsy on entry and were randomly assigned to daily estrogen plus progestin (given as one pill) or placebo (no hormones) and followed over a period of 13 years.
The researchers found that there was a statistically significant reduction in endometrial cancer incidence, after 5.6 years' median intervention and 13 years' cumulative follow-up, in the group that received combination estrogen plus progestin therapy (33 cases, 0.06% yearly) compared to those who received the placebo (95 cases, 0.10% yearly). "Continuous combined estrogen plus progestin use for 5.6 years in postmenopausal women with normal endometrial biopsy at therapy initiation resulted in a statistically significant reduction in endometrial cancer incidence, with the difference becoming statistically significant during longer-term post intervention follow-up," the authors write, adding that, "in postmenopausal women, continuous combined estrogen plus progestin use reduces endometrial cancer incidence by 35%."
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Continuous Combined Estrogen Plus Progestin and Endometrial Cancer: The Women's Health Initiative Randomized Trial, DOI: 10.1093/jnci/djv350