Geraldine Boggs, a Washington, D.C., nurse, poses for a photograph Monday in Washington. Boggs is a participant in a landmark government study about new cancer risks appearing in postmenopausal women after they stop taking hormones, while heart problems linked with the pills seem to fade. Boggs said women should pay attention to the new results.

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 of Stanford University, who chairs 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.

All the same, 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 for cancer, especially breast cancer, she said.

“The important message is women really need to make sure they continue getting their mammograms,” Stefanick 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,”‘ said Stefanick. 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 that the Women’s Health Initiative had not only found that 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 of women 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.

The study involved 15,730 postmenopausal women ages 50 to 79 who took estrogen and progesterone for an average of 5.6 years. The researchers analyzed the data for an average of 2.4 years after they stopped and found that the risk of heart disease and blood clots dropped back to about the same level as in women who had been taking a placebo. The risk of stroke also appeared to fall, but that finding was somewhat less clear.

The benefits of hormone treatment – a lower risk of colorectal cancer and bone fractures – also appeared to dissipate.

But the researchers were surprised to find that the overall risk of cancer was 24 percent higher in women who took hormones compared with those who an inert placebo: 281 of those who had taken hormones developed some type of cancer, compared with 218 in the placebo group. That appeared to be driven by a 27 percent increased risk of breast cancer, although that difference did not meet a test of statistical significance. There were 79 breast cancers in the hormone group, compared with 60 in the placebo group.

Stefanick said she believed that “breast cancer is really driving” the overall increased cancer risk.

“People were under the impression that once you stop the hormones your risk for breast cancer goes down,” Stefanick said. “This is saying, ‘No that’s not the case.’ It continues. It is bad news.”