As reported in the Journal of Clinical Oncology by Rowan T. Chlebowski, MD, PhD, and colleagues, long-term follow-up of the Women’s Health Initiative trial showed no benefit of treatment with estrogen plus progestin in reducing the risk of colorectal cancer in postmenopausal women.
Rowan T. Chlebowski, MD, PhD
Study Details
In the Women’s Health Initiative trial, 16,608 postmenopausal women (aged 50–79) with a uterus were randomly assigned to receive daily conjugated equine estrogen (CEE) at 0.625 mg plus medroxyprogesterone acetate (MPA) at 2.5 mg (CEE/MPA group, n = 8,506) or placebo (n = 8,102).
The current report provides outcomes after 24-year follow-up.
Study Details
The intervention ended after a median of 5.6 years. At that time, colorectal cancer was diagnosed in 43 patients in the CEE/MPA group vs 72 patients in the placebo group—a difference of 47% (P = .003). However, a higher proportion of cancers in the CEE/MPA group had lymph node–positive disease (59.0% vs 29.4%, P = .003).
After cumulative 24-year follow-up, colorectal cancer had been diagnosed in 215 patients in the CEE/MPA group (annualized rate of 0.15%) vs 216 patients (annualized rate of 0.15%) in the placebo group (hazard ratio [HR] = 0.95, 95% confidence interval [CI] = 0.79–1.15). A nonsignificant increase in colorectal cancer death was observed in the CEE/MPA group (87 patients [annualized rate = 0.049%] vs 69 patients [annualized rate = 0.041%]; HR = 1.20, 95% CI = 0.87–1.65, P = .26).
Vaginal bleeding (54.1% vs 5.2%) and breast changes (9.2% vs 2.0%) were more common in the CEE/MPA group during the first 6 months of treatment. In an analysis adjusting for vaginal bleeding and breast changes, bowel examinations were significantly delayed in the CEE/MPA group (P = .005), which may have contributed to delay in diagnosis.
The investigators concluded: “Taken together, the findings suggest no clinically meaningful benefit for about 5 years of CEE plus MPA use on colorectal cancer outcome.”
Dr. Chlebowski, of The Lundquist Institute, Torrance, California, is the corresponding author of the Journal of Clinical Oncology article.
Disclosure: The Women’s Health Initiative program is funded by the National Heart, Lung, and Blood Institute; the National Institutes of Health; and the U.S. Department of Health and Human Services. For full disclosures of the study authors, visit ascopubs.org.
