Women in Israel who used hormone replacement therapy (HRT) during and after menopause had about a 63 percent reduced risk of getting colon or rectal cancer. However, those women who were active in sports or who took aspirin regularly didn't benefit from HRT. As part of the Molecular Epidemiology of Colorectal Cancer (MECC) study, researchers questioned 2,400 Northern Israeli women with colon or rectal cancer about their use of hormone replacement therapy, using either pills or patches.  They matched the women with cancer to a control group with similar backgrounds. They also asked about use of aspirin, statins, and non-steroidal anti-inflammatory drugs (NSAIDS).  Women answered diet and exercise questions, including whether or not they ate 5 or more vegetables daily or took part in sports. Women with at least one first degree relative who had been diagnosed with colorectal cancer were listed as having a family history. Reduction in risk remained the same between women with and without familycolorectal cancer history, those who ate more vegetables and those who didn't, women with normal weight and obese women, and users and nonusers of statins. There was a stronger advantage to using hormone replacement therapy for women who were sedentary. However, women who were daily aspirin users and also took hormone replacement therapy had an increased risk of colorectal cancer. Women who used HRT and took part in sports had no advantage from HRT, but also did not have an increased risk. Even after adjusting for known risk factors for colorectal cancer -- age, use of aspirin/NSAIDs, use of statins, vegetable consumption, sports activity -- using hormone replacement therapy continued to have a significant effect in reducing the risk of colorectal cancer in this group of women. Significantly, only the use of combined estrogen/progestin HRT in pill form reduced colorectal cancer risk.  Estrogen alone or HRT patches did not. Writing in the Journal of Clinical Oncology, Gad Rennert, MD, and his team concluded,
The use of oral HRT was associated with a 63% relative reduction in the risk of colorectal cancer in postmenopausal women after adjustment for other known risk factors. This effect was not found in aspirin users and women with intensive sports participation.
SOURCE: Rennert et al, Journal of Clinical Oncology, published online ahead of print, August 24, 2009.

What This Means for Patients

Although use of hormone replacement therapy reduces risk for colorectal cancer in this study, other research has found that HRT increases risk for cardiovascular disease and breast cancer. Combining daily aspirin and hormone replacement therapy may increase your risk for colorectal cancer, and if you are very active in sports, you may not have any further benefit from HRT. Discuss your personal and family risks for heart disease, breast and ovarian cancer, and colorectal cancer in deciding how to use hormone replacement therapy.

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