Estrogen alone doesn’t raise breast cancer risk

Taking estrogen alone does not increase the risk of breast cancer in menopausal women, according to a large federal study that offers reassurance to millions of women using the hormone to quell hot flashes and other symptoms.

The seven-year study of more than 10,000 women, the biggest, best-designed study to examine the risks of hormone therapy, found no evidence that estrogen alone increased the danger of developing the common malignancy and produced evidence it may protect some women against the tumors. Earlier research had indicated the hormone raised the risk.

The findings apply only to women who can safely take estrogen alone because they have undergone a hysterectomy, but they are the largest group of hormone users – about 3.5 million of the estimated 4.4 million American women using some form of hormone therapy.

Experts cautioned that no one should take estrogen alone to reduce their risk for breast cancer because the hormone carries other potential dangers. Women should still use the lowest possible dose of hormone therapy for the shortest possible time, they said. But the findings help alleviate a major concern about using estrogen for short-term relief of menopausal symptoms, they said.

“The jury is now in: Estrogen does not increase the risk for breast cancer, which is what most women thinking about using the hormone worry about,” said Marcia Stefanick of Stanford University, who led the analysis being published today in the Journal of the American Medical Association.