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The increased risk of breast cancer known to be associated with the use of hormone replacement therapy applies to all ethnicities, a new study finds.
Ever since the Women's Health Initiative study was halted in 2002, after investigators found that the women taking HRT had a higher incidence of heart attacks, strokes, blood clots and breast cancer, experts have known about the increased health risks.
But one of the unresolved issues has been whether women of all races were equally affected, since the majority of the WHI participants were white, explains study co-author Malcolm Pike, a professor of preventive medicine at the University of Southern California's Keck School of Medicine. His report appears in the Sept. 16 online issue of The International Journal of Cancer.
However, based on the new study, Pike says, the firm conclusion is that "every one of these ethnic groups has the same risk of breast cancer from HRT."
Pike's study evaluated more than 55,000 menopausal American women taking part in the Multiethnic Cohort Study. That study included more than 215,000 men and women, aged 45 to 75 at the start of the study, who were living in Hawaii or California in 1993. The women included whites, blacks, Hawaiians, Japanese-Americans and Latin Americans. "The women told us their contraceptive history, their pregnancy history, what hormones they took postmenopause," Pike says.
Current use of the estrogen-progestin therapy was associated with a 29 percent higher risk of breast cancer after five years of use, he found. The association held for women in all ethnic groups.
Current use of estrogen-only therapy was associated with a 10 percent higher risk of breast cancer after five years of use, and this was found in all ethnic groups except for blacks.
The researchers also found that leaner women -- those with a body mass index below 25 -- had a slightly higher relative risk of getting breast cancer than the heavier women, although the heavier women were also at increased risk. Although the researchers couldn't pinpoint the reason for the finding, Pike did have a theory.
"The bigger you are postmenopausally, the more estrogen you (continue) to make," he says. That's because the more fat cells a woman has, the more estrogen she produces.
A woman who weighs 180 pounds, for example, is probably making as much estrogen herself as the breast positively reacts to, Pike says. "These women are at a saturation point."
But the woman who weighs, say, 130 pounds or less gets more of an effect from supplementary estrogen, he says, perhaps accounting for their increased risk.
Studies following the halting of the WHI have been plentiful, all evaluating different aspects of risk. A study published last month in The British Medical Journal found that the risk of breast cancer declines with age if a woman is not taking HRT. But if she does take HRT, that risk starts to climb.
If therapy is stopped, however, the risk returns to that of a woman of the same age who has never used HRT, the researchers found.
Another expert, Roshan Bastani, associate dean for research at the University of California Los Angeles School of Public Health and Jonsson Comprehensive Cancer Center, praised the new research.
"I think it's a well-done study," she says. "And it is important, particularly because they were able to include data from large numbers of people from many ethnic groups."
For women, the study provides more valuable information, but each woman must still take into account her own symptoms, medical history and family background when deciding whether to take hormones after menopause, Pike and Bastani agree.
"What they need to do," Bastani says, "it to understand the risks, and then assess whether they are willing to take the risk."
For instance, she says, if a particular woman is told that taking hormones increases her risk of breast cancer or other disease by, say, 10 percent, she should ask what her "baseline" risk is, which depends on factors such as family background and medical history. If the baseline risk is just 1 percent or 2 percent, an increased risk is not a lot compared to a baseline risk of 50 percent or 80 percent.
"If you want to take HRT to deal with problems at menopause, it's perfectly reasonable," Pike says, as long as the treatment is limited. It's difficult, he says, to put an absolute number of years on that advice.
The best course, says Pike, is to keep the amount of progestin "to an absolute minimum.
"What a woman wants to do is discuss with her physician -- can she use the minimum amount of estrogen to control her hot flashes, and how frequently does she need to take progestin?"
c.2005 HealthDay News