The Women's Health Initiative (WHI) trial of estrogen plus progestin in postmenopausal women identified more overall health risks than benefits.
However, the use of estrogen plus progestin was associated with a significant decrease in the risk of colorectal cancer.
In this study, researchers evaluated any colorectal cancers that developed.
The WHI trial included 16,608 postmenopausal women, aged between 50 and 79 years, with an intact uterus. The women were randomly assigned to a combination of conjugated equine estrogens plus medroxyprogesterone acetate, or placebo.
|Cancers were similar in histology and grade.|
|New England Journal of Medicine|
The main outcome measures in this study were the incidence, stage, and type of colorectal cancer.
The research team found that there were 43 invasive colorectal cancers in the hormone group compared with 72 in the placebo group (hazard ratio, 0.56).
They established that the cancers in the hormone group were similar in histology and grade to those in the placebo group. However, the cancers in the hormone group had a greater number of positive lymph nodes and were more advanced.
Dr Rowan Chlebowski and colleagues concluded, "Relatively short-term use of estrogen plus progestin was associated with a decreased risk of colorectal cancer".
"However, colorectal cancers in women who took estrogen plus progestin were diagnosed at a more advanced stage than those in women who took placebo".