|Scrutinizing the evidence for breast
cancer procedures and treatments
Two Articles Challenge Recent HRT Reports
DECREASED BREAST CANCER RATES AND HORMONE REPLACEMENT
THERAPY USE: ARE THEY RELATED?
by Patricia Kelly, PhD
Recent reports attribute the drop in US breast cancer rates between
2002 and 2003 to a decline in the use of hormone replacement therapy
(HRT). However, evidence from multiple sources suggests that changed
HRT use is unlikely to result in lower breast cancer rates, since:
Decreased breast cancer rates occurred in women of all ages, not only
those of menopausal age, who most frequently use HRT. The change in
rate was greater for older than younger women, perhaps due to an
improved ability to track changes in the older group, which included the
vast majority of breast cancers.
Decreased breast cancer rates were found in women with ER negative
as well as ER positive breast cancers. A greater change was found for
ER positive tumors, perhaps due to an improved ability to track changes
in the ER group, which included the vast majority of all breast cancers.
Some reports speculate that estrogen causes ER positive breast
cancers to grow, so the decline in HRT use resulted in a greater
decrease in ER positive than ER negative tumors. The issue, however, is
whether HRT use leads to tumor growth beyond what might result from a
womanâ€™s own hormones. In this regard, over 15 studies find that
breast cancers detected in women using HRT at the time of their
diagnosis were not growing more rapidly than cancers detected in non
HRT users. If HRT use did significantly influence breast cancer growth
rates, tumors in HRT users would have grown more rapidly than those of
non HRT users. No such increase in growth rate was found. These
scientific results do not support the theory that HRT use itself causes
breast cancers to grow.
Other scientific studies have investigated breast cancer risk after
women stop using HRT. At least nine studies find NO significant
decrease in breast cancer risk when HRT use stops, even up to ten
years later. (Risks were not increased either.)
In Canada, where many women also stopped taking HRT in 2002, NO
decrease in breast cancer rates has occurred. If declining HRT use were
a likely cause of reduced US breast cancer rates, those in Canada
should also have dropped. They did not.
In conclusion, the cause(s) of decreased breast cancer rates from 2002
to 2003 are currently unknown, but do not appear to be the result of
changes in HRT use. Reduced breast cancer rates in women of all ages
and with different tumor types, studies finding no reduction in breast
cancer risk even ten years after HRT use stops, and the lack of a decline
in Canadian breast cancer rates, all suggest that factors unrelated to
HRT use are responsible for the drop in US breast cancer rates from
2002 to 2003.
HRT: Recent Study Results In Perspective
by Patricia Kelly, PhD
You may have heard that the Women’s Health Initiative (WHI) study
conclusively showed that women who took Prempro, a type of hormone
replacement therapy, had an increased breast cancer risk and no
reduced cardiovascular disease risk. A closer look suggests that
differences between the women who did and did not take Prempro may
be due to other causes, not Prempro.
The study found an exceedingly small difference in breast cancer risk
between those who did and did not take Prempro – 8 in 10,000 women a
year, or eight hundredths of one percent. Even this small difference is
unlikely to be due to hormone use, however.
Most breast cancers are thought to take over eight years to be
detected. Therefore, a breast cancer that started in the first year of the
study, after a woman started taking Prempro, would probably not be
found for eight or more years. The study followed women for only about
five years, so all or most of the reported breast cancers were probably
present, but undetected, before the study began.
It is unlikely that Prempro caused breast cancers to grow more rapidly
and be detected sooner. A number of studies have found that women
who were using hormones when their breast cancers were detected did
not have larger or more rapidly dividing cancers than women who were
not taking hormones when their breast cancer was found.
The very small annual differences in cardiovascular disease – 7 cases of
heart disease and 8 of stroke per 10,000 women – are also unlikely to be
due to Prempro. In this study, most women started taking Prempro at an
average age of 63. Therefore, for ten or more years after menopause
most were without the cardiovascular benefits of replacement hormones
that other studies find. In these years, some may have developed
cardiovascular disease which couldn’t be corrected by taking Prempro
for an average of five years. The cardiovascular disease risks found in
this study apply to women who start using hormones ten or more years
after menopause, not to women who begin using hormones at
In the WHI study a woman’s risk was assessed as if she were taking
Prempro throughout the study, even if she stopped using it. A whopping
42% discontinued Prempro use during the study. Different risks may be
found when calculations are based on a woman’s actual Prempro use,
not a woman’s assigned use.
Most importantly, women who used Prempro did NOT have a higher
mortality than non-users. In fact, by the end of the study, Prempro users
began to have a lower mortality rate than non-users.
The Prempro regimen is one in which both a synthetic estrogen and a
progestin are taken every day. The results of this study therefore do not
apply to other, newer approaches in which more natural hormones are
used and in which a progestin is taken only part of the time.
The results of this and previous studies suggest that if hormone
replacement therapy increases breast cancer risk, it does so to a very
Recommended Web Site: www.ptkelly.com
Patricis Kelly, PhD, is the author of Assess Your True Risk of Breast
Cancer (Henry Holt, NY)
"The beauty of this book lies in the author's explanations on how
statistics are used and sometimes misused."
"In particular, it puts into context the statistics and "facts" on breast
cancer that are pervasive in the media and even in some doctors'
"Perhaps the greatest contribution of "Assess Your True Risk of Breast
Cancer" is the material on two controversial topics: hormone
replacement therapy and its connection to breast cancer, and the
meaning of a diagnosis of "ductal carcinoma in situ."
SHARI ROAN, LA Times
Web page updated July 3, 2009