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WHI Intranet Site
Effects of Estrogen plus Progestin on Colorectal Cancer
Dietary Trial (1994-2005)
Hormone Trials (1994-2004)
Calcium/Vitamin D Trial (1994-2005)
Observational Study (1994-present)
Estrogen plus Progestin Effects on Colorectal Cancer and its Diagnosis
Frequently asked questions
Abstract of scientific paper in the New England Journal of Medicine
Early WHI study findings on the effects of taking combined estrogen plus progestin (E+P) were published in July 2002. The E+P study continues to be analyzed. In the March 4, 2004 issue of the New England Journal of Medicine, there are updated results on colorectal cancer cases, and the types of cancer for women in the study.
The 2002 reports showed that fewer women taking E+P had colorectal cancer than those taking placebo (inactive) pills. This updated analysis shows that after an average of 5.6 years, 43 of the 8,506 E+P women and 72 of the 8,102 women on placebo developed colorectal cancer. Of the total cancers, 115 cases were invasive cancers which have a greater chance of spreading to other parts of the body. From these cases, we learned:
Because of E+P use, there were 6 fewer cases of colorectal cancer for every 10,000 women over one year.
Overall, there was a 44% decrease in the risk for colorectal cancer due to E+P.
The colorectal cancer in the E+P group had similar characteristics (looked the same under a microscope) to those in the placebo group. However, the tumors in the E+P group tended to be more advanced (had spread to the lymph nodes or elsewhere in the body).
Colorectal cancer diagnosed in the E+P women were more advanced (regional/metastatic) in 76 percent of cases versus 49 percent on placebo.
A more advanced stage is usually associated with a poorer outcome. At this time, no direct statements can be made about the prognosis of colorectal cancers found in women taking E+P until more follow-up information is collected.