Note: this issue of a protective effect was known at the time the original WHI study information was published but also received very little attention
New study confirms HRT helps ward off colon cancer
Millions of women stopped taking HRT when a Women's Health Initiative study showed in 2002 that the hormones raised the risk of stroke, heart disease and breast cancer.
But the Women's Health Initiative had also found that HRT protected against colon cancer. Some studies have also suggested that oral contraceptives might reduce the risk of the disease, while the fact that women are at lower risk of colon cancer than men also hints at a hormonal role in disease risk.
To investigate ties between HRT and colon cancer further, Dr. Millie D. Long of the University of North Carolina at Chapel Hill and her colleagues matched 443 women diagnosed between 2001 and 2006 with distal large bowel cancer (meaning tumors at the far end of the colon and the rectum) to 405 healthy control women. The average age of the study participants was around 63.
Long's team found that women who had ever used HRT were at half the risk of this type of colon cancer compared to women who'd never used hormone replacement, and the longer a woman was on HRT, the lower the risk.
For example, women who used hormones for less than four years cut their colon cancer risk by about one-quarter; four to eight years of HRT cut risk by a third; nine to 14 years of use halved risk; and 15 years or more of HRT reduced risk by two-thirds. The effects were the same for African-American women and white women.
However, there was no relationship between oral contraceptive use and colon cancer risk, the study team reports in the American Journal of Gastroenterology.
Long-term hormone therapy is no longer recommended for postmenopausal women, Long and her team note, although it is still sometimes prescribed on a short-term basis to help women with menopausal symptoms such as hot flashes. The major drop off in distal large bowel cancer in recent years could have been related to widespread use of HRT, the researchers say.
More research is needed to determine if HRT's protective effects persist after women stop taking hormones, the researchers add, or whether there might be a "rebound" effect with more pre-cancerous polyps developing after a woman halts
HRT.
"It may become important in the future to tailor timing of women's colorectal screening based on cessation of hormonal therapy," Long and her colleagues conclude.
SOURCE: The American Journal of Gastroenterology, online March 30, 2010.
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