Are Breast Cancer Rates Really Going Down

Every year at this time, cancer doctors and researchers gather at the annual Breast Cancer Symposium in San Antonio, Texas, to hear the latest news in the field. This year we heard surprising news from investigators at M.D. Anderson: there was an overall 7 percent relative decline in diagnosed cases of breast cancer between 2002 and 2003. The number of breast cancer cases had increased in the 20 years before 2002. The steepest decline – 12 percent – occurred in women between ages 50 and 69 diagnosed with estrogen receptor positive (ER-positive) breast cancer. ER-positive breast cancer depends on hormones for tumor growth. One reason for the decline, according to the researchers, may be the 2002 announcement that hormone replacement therapy (HRT) is a major contributor to breast cancer growth. The announcement led thousands of women to stop taking these drugs. Although the researchers aren’t 100 percent sure that stopping HRT is the only reason for the decline, Peter Ravin, Ph.D., the study’s senior investigator, says “it makes perfect sense” if you consider that use of HRT may be an important contributing factor to breast cancer development. “Research has shown that ER-positive tumors will stop growing if they are deprived of the hormones, so it is possible that a significant decrease in breast cancer can be seen if so many women stopped using HRT,” he says. This news isn’t to be confused with the actual number of breast cancers diagnosed each year, though. Unfortunately, that number has continued to climb. The number of women in the target age group above swelled dramatically as baby boomers came into midlife. As the denominator swelled, so did the numerator, the number of breast cancers diagnosed. This number includes new cases as well as recurrences of breast cancer in women previously diagnosed. The big news comes from the fact that researchers expected a larger numerator and instead saw a reduction. So is not taking HRT the answer? I don’t know. There are several other issues that came to my mind when I read this breaking news. Here are a few: • Is the 2002 announcement that HRT contributes to breast cancer the most important reason for the decline in new breast cancer cases? Or are more women not taking HRT because fewer hysterectomies (removal of the uterus) and more hysteroscopies – a procedure that examines and removes masses from the uterus without the need for a hysterectomy – are taking place, avoiding the need for HRT? • Because HRT increases breast density, which makes it harder to image breast tumors, discontinuing it should improve detection of breast cancers that previously were hidden in the image. How does that get factored in? • Breast cancer takes several years to grow, so stopping HRT for a year or less won’t necessarily prevent someone from getting it; the tumor will be smaller when detected because it’s been fed for a shorter time. • What about high-risk women who are taking tamoxifen or raloxifene to prevent breast cancer? What do those statistics look like? Are there more women doing this and what impact might it have on breast cancer rates? • How many women in the 50 to 69 age group had screening mammograms in 2003? Is that up, down or the same as 2002? All of these factors may also have influenced the reduction. So, although the news certainly is exciting, I want to learn more before I hang my hat (or my bra) on the HRT reduction hypothesis.