The lead author of a breast cancer study says it shows that women who take estrogen-only pills less than ten years "don't have to panic."

But the cancer specialist says "longer-term users" should look at alternatives. The Nurses' Health Study finds women who take estrogen for at least 15 years have a much higher risk of getting breast cancer.

Researchers say the findings should be reassuring for women who want to use the hormone for a short time to relieve symptoms of menopause.

The study appears in today's Archives of Internal Medicine.

A Women's Health Initiative study in 2002 found estrogen-progestin supplements carried an increased risk of breast cancer, strokes and heart attacks. That led millions of American women to stop taking them.

Another Women's Health Initiative study of estrogen alone found other health problems, but no higher risk of breast cancer among women who had taken it for seven years.