Scrutinizing the evidence for breast
cancer procedures and treatments

    Two Articles Challenge Recent HRT Reports


    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
    woman’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
    small extent.

    Recommended Web Site:

    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
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