Hormone Therapy associated with reduced
Colorectal Cancer Risk
Newswise — The combination of estrogen plus progestin,
which women stopped taking in droves
following the news that it may increase
their risk of breast cancer, may decrease
their risk of colorectal cancer, according
to a report published in the January issue
of Cancer Epidemiology, Biomarkers and
Prevention, a journal of the American
Association for Cancer Research.
“Compared to women who had never taken these hormones, the
use of estrogen plus progestin was
associated with a reduced risk of colorectal
cancer,” said Jill R. Johnson, M.P.H., a
doctoral student at the University of
Minnesota School of Public Health.
The largest risk reduction, approximately 45 percent, was
seen among women who had completed use of
estrogen plus progestin five or more years
previously.
Johnson and her colleagues extracted data from 56,733
postmenopausal women who participated in the
Breast Cancer Detection Demonstration
Project follow-up study.
Hormone therapy use and other risk factors were ascertained
through telephone interviews and mailed
questionnaires between 1979 and 1998.
During an average 15 years of follow-up, Johnson and
colleagues identified 960 new cases of
colorectal cancer in this population.
Any use of estrogen therapy was associated with a 17
percent reduced risk in colorectal cancer.
Among those who used estrogen, the largest reductions were
seen among those who were current users (25
percent reduced risk) and users of ten or
more years duration (26 percent reduced
risk).
Researchers also found a 22 percent reduced risk among
those who had ever used estrogen plus
progestin in combination.
They further found a 36 percent reduction in risk among
those who had used progestin sequentially or
less than 15 days per month.
Past users of estrogen plus progestin, who had stopped at
least five years ago, had a 45 percent risk
reduction.
Although Johnson’s study was not designed to look at
biological mechanisms for the protective
effect of estrogen therapy, she did say that
previous research has suggested that
hormones may play a role in decreasing
levels of insulin-like growth factors,
thereby reducing risk.
“The biological mechanism will need to be explored in
further studies,” said Johnson.
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