Women taking hormone drugs during or around menopause have a higher risk of developing breast cancer than those who wait five years, according to a study of more than 1.1 million British patients.
The magnitude of the risk was also linked to the type of hormone replacement therapy the women took, researchers said today in the Journal of the National Cancer Institute, an Oxford University Press publication not affiliated with the U.S. National Cancer Institute.
The study updates research that showed a link between the therapy, known as HRT, and breast cancer risk, and is the first to investigate the timing of the treatment. A tie between hormone type and risk had been suggested by the U.S. Women’s Health Initiative, a set of clinical trials and a study of health records for 161,808 postmenopausal women.
“What we found and what had been suggested earlier is that if you start taking HRT at or around menopause, the risks of breast cancer are higher,” said Valerie Beral, lead researcher for the latest study and director of the cancer epidemiology unit at Oxford University in Oxford, England, in a telephone interview today. “It’s not only the interval, it’s also the kind of HRT the women are taking.”
The study found that about 55 percent of the 1.1 million women in the study, recruited from 1996 to 2001, reported taking hormone therapy at some time in their lives.
Among women in their 50s who never took hormones, the annual rate of breast cancer was 3 per 1,000 in the study. There was little to no increased risk for women getting estrogen alone at the time of study if they had started the therapy at least five years after menopause. If they had begun estrogen alone less than five years after menopause, their risk increased to 4.3 breast cancers per 1,000.
Women who had started the combination of estrogen and progestin less than five years after menopause showed a rate of 6.1 per thousand, about double the risk of never-users, the results showed.
“We’ve known for a while that HRT can increase the risk of breast cancer,” said Ed Yong, head of health information for Cancer Research UK, a London-based charity, in an e-mailed message today. “This study suggests that there might be some situations in which that risk is small or negligible.”
Delaying HRT therapy to minimize risk may not be feasible, because hormones are usually prescribed to alleviate symptoms during menopause, not five years later, Beral said.
Reduced estrogen levels during menopause may cause the part of the brain responsible for temperature control to malfunction, according to the North American Menopause Society, a nonprofit organization based in Mayfield Heights, Ohio. Hot flashes strike suddenly and can be accompanied by rapid heartbeat, nausea, dizziness, headaches, muscle weakness and fatigue, according to the group.
Wyeth, acquired in October 2009 by New York-based Pfizer Inc. for $68 billion, is the largest maker of hormone replacement drugs. Annual sales of Wyeth’s hormone-replacement drugs topped $2 billion before results from the Women’s Health Initiative released in 2002 suggested women using the medicines had a higher breast cancer risk.
The National Cancer Institute, based in Bethesda, Maryland, estimates that there were 209,000 new cases of breast cancer in the U.S. last year, and about 40,000 deaths from the disease.