Washington —- Menopausal women who took estrogen and progesterone faced a small increased risk for cancer for more than two years after they stopped, according to the latest results of a major federal study that has revealed a series of sobering findings about the once-popular hormone therapy.

The study of more than 15,000 women who took the hormones for more than five years found that the chance of developing cancer remained elevated well after they quit, which many did after an earlier stage of the study showed that the risks outweighed the benefits.

While their increased risk of heart attacks, blood clots and strokes appeared to vanish as soon as women got off the drugs, the cancer risk persisted. It appeared to be driven primarily by a continued increased rate of breast cancer but also by a new, unexpected higher risk of other malignancies, such as lung cancer, the analysis found.

"The question has been: Do the risks persist?" said Marcia Stefanick, chairwoman of the steering committee for the federally funded Women's Health Initiative. "What this clearly shows is, unfortunately, the risk for cancer continues."

Stefanick said the data appeared to show a real trend even though the breast cancer difference was not statistically significant, but other experts warned that finding could have been due to chance.

The findings underscore the now-standard recommendation that women who take hormones to relieve hot flashes and other effects of menopause should use the lowest possible dose for the shortest time. Stefanick said. And the millions of women who have taken the hormones should be monitored closely, she said.

It remains unclear how long the increased risk persists, she said, and researchers have continued following the women to try to answer that crucial question.

"This says, 'You're not quite safe yet, but let's hope you'll be safe soon,' " Stefanick said. It is also unclear whether women who took the hormone combination for shorter periods or took estrogen alone face similar ongoing risks.

For years, doctors recommended that women take hormones to alleviate the symptoms of menopause and in the belief that the drugs would protect their hearts. But in 2002 researchers stunned doctors and women when they reported the Women's Health Initiative had not only found the hormones did not protect the heart but actually increased the risk of heart attacks, strokes, blood clots and breast cancer.

The news prompted millions to stop taking the hormones, but until the new report, published in today's issue of the Journal of the American Medical Association, no one knew whether the higher risks would continue nevertheless.