MONDAY, Nov. 3, 2003 (HealthDayNews) -- A new study suggests women who develop breast cancer while on hormone therapy should stop the drugs because researchers found tumors that grow more rapidly in the presence of estrogen become more tame when the hormone is withdrawn.
When hormone replacement therapy (HRT) is stopped, the tumors "stop growing," says study leader Dr. Nigel Bundred, a breast cancer expert at South Manchester University Hospital in England.
The vast majority of breast cancers in women on HRT are sensitive to estrogen, and the hormone stimulates tumors that might otherwise remain hidden, Bundred says. Doctors can easily determine if a tumor responds to estrogen using tissue taken at the time of biopsy to see if the cells are indeed cancerous.
By now it's well known that hormone therapy, and estrogen in particular, slightly increases the risk of breast cancer in women who take the drugs. Less clear is what women on estrogen should do if they develop a breast tumor.
The effect of HRT on cancer cells is similar to that of the drug tamoxifen and other so-called anti-estrogen cancer drugs, Bundred says.
In the United States, halting estrogen therapy is the common course for women newly diagnosed with breast cancer. But occasionally, and in certain other countries, doctors may continue HRT in these patients because suddenly stopping the drugs can lead to an uncomfortable rush of hot flashes, vaginal dryness and other symptoms of menopause for which women take estrogen.
The latest study, reported in the Dec. 15 issue of Cancer and available online Nov. 3, indicates that practice might be harmful. However, at least one recent study found women who continued HRT after a diagnosis of breast cancer didn't fare any worse than those who stopped taking hormones. "We didn't have any adverse outcomes in terms of breast cancer," says Dr. David Decker of William Beaumont Hospital in Royal Oak, Mich., who led that work.
Decker is willing to let women on HRT continue treatment after breast cancer turns up, but admits he's in the minority in this country and that most doctors cease the hormones immediately. Still, "there are some patients who just have a crummy quality of life" when they stop taking estrogen.
In the British study, Bundred's group looked at 140 women treated for breast cancer in England between 1996 and 2000. All had been taking HRT at the time of their diagnosis, but 125 immediately stopped the hormones upon learning they had cancer. The rest continued taking HRT until they had surgery to remove the cancer, a period lasting up to about a month. The researchers also studied 55 other women with breast cancer who weren't taking HRT, using them as a control group.
Of the 125 women who stopped HRT, 106 (about 85 percent) had breast tumors that were sensitive to estrogen. Twelve of the 15 women who continued taking hormones had such cancers.
Cancers that grew faster in the presence of estrogen slowed down markedly in the women who stopped taking HRT between diagnosis and surgery, judging by several molecular markers of tumor growth. Those that weren't estrogen-sensitive didn't wind down, and for women with these cancers continuing HRT won't make a difference, Bundred says.
Breast cancer is the second most common cancer in women, behind skin cancer. This year, roughly 211,000 American women will be diagnosed with the disease, according to the American Cancer Society, and nearly 40,000 will die from it.