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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 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 menopause. 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: 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' offices." "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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