That is the primary message women should take away from the latest study from the Women's Health Initiative (WHI) on the relationship of estrogen and progestin replacement and colon cancer, said study co-author Jean Wactawski-Wende, Ph.D., from the University at Buffalo.
Results of the study, which appeared in the March 4 issue of The New England Journal of Medicine, showed that while there were fewer colon cancers among women in the treatment group than among women taking a placebo, colon cancers that did develop in the treatment group were more advanced when diagnosed, suggesting a poorer outcome.
Wactawski-Wende, second author on the study, co-directs UB's WHI Vanguard Center and is an assistant professor of social and preventive medicine and gynecology and obstetrics. "The results of the current study that show more advanced cancers in the treatment group are somewhat puzzling," said Wactawski-Wende. "We think it's possible that women receiving estrogen and progestin may have attributed colon cancer symptoms, such as constipation, diarrhea, cramping or stomach pain, to the hormone treatment, and delayed cancer screening. Or they may have been distracted from reporting potential symptoms of colon cancer by symptoms related to their HRT therapy, such as vaginal bleeding.
"It's also possible that the hormone treatment only prevents pre-cancerous lesions from progressing," she said. "Study participants weren't screened for colon cancer when they entered the study, and colon screening wasn't part of the WHI activities, so we don't know if those who were diagnosed with colon cancer during the study already had cancerous polyps."
The current study updates findings from the WHI on colorectal cancer reported in 2002, when the estrogen plus progestin replacement trial was halted. The study was stopped because, contrary to expectations, data showed that the overall impact of the treatment on the health of postmenopausal women was not positive. Both the initial and current study of estrogen plus progestin reported a positive impact on colorectal cancer risk, however.
The updated analysis showed that, among the 8,506 women in the study, there was a 44 percent decrease overall in the risk of colorectal cancer in the estrogen plus progestin group, or 6 fewer cases per 10,000 women treated per year.
However, 76 percent of the colorectal cancers in this group were more advanced (had spread to other parts of the body) versus 49 percent in the women receiving a placebo. "These results give us one more reason to talk about the importance of screening and colonoscopy," said Wactawski-Wende. "All women should consider a colonoscopy after 50, whether or not they take hormones."
WHI researchers will continue to follow all the women in the study to learn more about the effects of hormone replacement on colorectal cancer, she said.
Additional primary authors on the study were Rowan T. Chlebowski, M.D., Ph.D., from Harbor-UCLA Research and Education Institute; Cheryl Ritenbaugh, Ph.D., M.P.H., from Kaiser Permanente Center for Health Research, Portland, Ore.; F. Allan Hubbell, M.D., M.S.P.H., from the University of California-Irvine; Joao Ascensao, M.D., Ph.D., from George Washington University; Rebecca J. Rodabough, Victoria M. Taylor, M.D., M.P.H., Chu Chen, Ph.D., and Emily White, Ph.D., from Fred Hutchinson Cancer Research Center; Carol A. Rosenberg, M.D., from Evanston Northwestern Healthcare; Randall Harris, M.D., Ph.D., from Ohio State University, and Lucile L. Adams-Campbell, Ph.D., from Howard University Cancer Center.
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