Evidence Mounts on HRT Breast Cancer Dangers

Yet another study was released earlier this month showing that women who use combination hormone replacement therapy drugs face much greater risks of developing certain types of breast cancer. This latest study from researchers at the Fred Hutchinson Cancer Research Center noted that women taking HRT drugs had a four-fold (400%) increased risk of developing lobular breast cancer and was the first study to focus on lobular cancers and include a review of pathology reports and tissue from tumors (http://seer.cancer.gov/data/). A statistically significant increased risk of ductal-lobular invasive cancers was also noted. This study is also particularly noteworthy in that it found that users of combination HRT drugs (containing estrogen and synthetic progestin) were at significantly increased risk after only three years of exposure, helping to dispel the notion that these drugs are safe if taken for less than 5 years.

Lobular breast cancers are relatively rare, representing only 15% of invasive breast cancers. Unfortunately, lobular cancers are quite virulent in that they are more difficult to detect through mammography and are more likely to be first diagnosed at later stages. Researchers have noted for quite some time, however, that lobular cancers appear to be more prevalent in women who used combination hormone replacement therapy drugs, such as Prempro and Provera taking in combination with Premarin or other estrogen products. This study included 1,044 women (ages 55 to 74) who are part of a Washington State breast cancer registry and who were diagnosed with invasive breast cancer between 2000 and 2004.

Although rates of CHT [combined estrogen and progestin hormone therapy] use have dropped considerably since the publication of the WHI trials, studies of the risks associated with CHT use remain of critical importance given the estimated 57 million hormone therapy prescriptions that are still filled in the United States each year. The results of this study provide further evidence that CHT use increases the risk of ILC (invasive lobular cancer], and they indicate that current use of CHT for as little as 3 years may increase risk of these tumors substantially. Continued research aimed at identifying the biological basis for the relationship between CHT use and lobular carcinoma risk is warranted.