New government numbers give some of the strongest evidence yet that menopause hormones can raise the risk of breast cancer. Rates of the disease leveled off in 2004 after plunging in 2003, the year after millions of women stopped taking hormones because a big study tied them to higher heart, stroke and breast cancer risks.

From 2001 to 2004, breast cancer rates fell almost 9 percent - a dramatic decline. The trend was even stronger for the most common form of the disease - tumors whose growth depends on hormones. Those cases fell almost 15 percent among women ages 50 to 69, the group most likely to have been on hormone pills.

“The story has gotten stronger,” says Peter Ravdin, a biostatistician at the University of Texas M.D. Anderson Cancer Center in Houston who led the research, which was published in this week’s edition of The New England Journal of Medicine.

Some were skeptical several months ago, when Ravdin and National Cancer Institute researchers first reported the 2003 drop and tied it to hormone use. The new numbers, which add 2004, prove this was no fluke, says Julie Gralow, a spokeswoman for the American Society of Clinical Oncology and cancer expert at the University of Washington in Seattle.

“Because it didn’t bump back up again,” it supports the idea that the rate has stabilized at a new lower level, says Gralow, who wasn’t involved in the study.

Brenda Edwards, one of the journal authors who is a National Cancer Institute researcher, agrees: “Now we have a statistically significant decline” over three years and clear proof of a trend.

Although some recent analyses suggest the heart risks are not as great as had been believed for younger, newly menopausal women, the statistics out this week add to the worries about cancer. After rising steadily through the 1990s, the breast cancer rate dipped from 2001 to 2002, from 138 cases to 135 cases per 100,000 women. After the federal Women’s Health Initiative study reported in July 2002 on the health risks of hormones, use of the pills plunged.

“Reports such as this cause confusion,” says Joseph Camardo, Wyeth’s senior vp of global medical affairs. “The hypothesis put forth in this report does not change what we know about hormone therapy, which is based on data from numerous, more rigorous studies including the Women’s Health Initiative. These randomized trials provide a higher level of evidence on the risk/benefit profile of hormone therapy.”

One possible factor contributing to the decrease in breast cancer incidence reported in 2003 could be a decline in mammography screening during the same time period, he offerse. If this decline represents a decrease in early cancer detection, it may only become apparent in the coming years as these cancers manifest and are detected at a later more aggressive stage.

Further reading…
The Associated Press;
New England Journal of Medicine article;
Wyeth’s response.[tags]Breast Cancer, Hormone Replacement Therapy, Prempro, Wyeth[/tags]