Report Incites Controversy After Breast Cancer Decline Linked to HRT Use

CURE, Spring 2007, Volume 6, Issue 2

The medical community strikes up a debate after a 2006 study released data linking the decreased use of hormone replacement therapy to the recent decrease in breast cancer cases.

When the Women’s Health Initiative reported in July 2002 the link between hormone replacement therapy, or HRT, and increased risk of breast cancer, the medical community and millions of women had their worlds rocked.

These findings were substantially underscored in December 2006 at the annual San Antonio Breast Cancer Symposium. There, researchers from M.D. Anderson Cancer Center in Houston presented an analysis that found 14,000 fewer U.S. women were diagnosed with breast cancer in 2003 than in 2002, and that the drop was attributable to reduced HRT use.

The decrease from 203,500 breast cancer cases in 2002 represents a 6.9 percent overall drop, and a whopping 12 percent drop among women ages 50 to 69 with estrogen receptor-positive breast cancer—the variety fueled by estrogen. Diagnosis rates had been steady for the preceding few years.

However, like any ground-breaking news, the population study was met with debate. Some breast cancer research leaders question whether the information is conclusive, and warn against dismissing positive trends in cancer prevention.

Since the late 1970s, tens of millions of women had been taking this common treatment—many for a decade or more. Commonly used by postmenopausal women, HRT was proven to reduce discomfort associated with menopause and health risks like osteoporosis caused by the natural drop in the hormones estrogen and progesterone.

By summer 2002, 30 percent of postmenopausal women were on some form of HRT. But one year after the WHI report made headlines, there was a 66 percent drop in prescriptions written for Prempro™, and a 33 percent drop for Premarin®—two popular HRTs.

Peter Ravdin, MD, PhD, research professor of biostatistics at M.D. Anderson and lead investigator of the population study, says such numbers suggest a connection between reduced HRT use and lower risk of breast cancer. “We observed a marked change in breast cancer rates in 2003 after numbers had been stable for the past few years,” Dr. Ravdin says. “The most obvious change was in use of HRT starting in July 2002.”

The significant decrease, as well as the number of patients affected, meant big news in San Antonio. While he agrees “hormone replacement is a very good hypothesis,” and the report offers “useful information,” Victor Vogel, MD, professor of medicine and epidemiology at University of Pittsburgh-Magee Women’s Hospital, worries the study is not conclusive since it does not randomly study the cause of the reduced breast cancer cases. Further, Dr. Vogel says the sensation the M.D. Anderson report caused could lead those who were watching their diets and getting regular mammograms to now disregard those practices. “I think we should always hold out to think we’re not as smart as we think we are,” he says.

He points to an alternative, or contributing, explanation to the drop—the high rate of mammograms throughout the early 2000s that caught early cancers, which were removed before developing into full-blown invasive cancers. Positive diet changes might be another factor, Dr. Vogel says. Others have suggested the lowered rates could be linked to increased use of the selective estrogen receptor modulator Evista® (raloxifene), prescribed for osteoporosis but recently proven to lower the risk of invasive breast cancer in high-risk women. The FDA is currently reviewing Evista for approval in this setting.

Dr. Ravdin believes news of the connection between HRT and breast cancer only heightens the message that individuals have the power of choice in their diet, exercise habits and whether to use HRT. “We have not absolutely proven why the drop in incidence occurred, but one thing that was good about our presentation is that it will cause a lot of other people to look into their data to see the effects of reducing HRT use.”

The WHI is scheduled to report more findings based on a randomized study by year’s end, says Dr. Ravdin. In addition, studies are currently under way in Canada and Europe that examine the effects of halting HRT use. “On one level, HRT research isn’t glamorous,” Dr. Ravdin says. “It’s not like curing cancer. But it is very important because it touches almost everybody directly or indirectly."