Children who survive cancer treatment face increased heart health risk and should take measures soon after life-saving therapy to reduce the risk of serious problems later in life, according to research presented at a major medical meeting.

The five-year survival rate from childhood cancer has soared from 58 percent in 1975 to 1977, to 83 percent in the period from 2003 to 2009.

While earlier research had shown that childhood cancer survivors face heart disease and other potentially serious health problems decades after treatment, a new study found that chemotherapy takes a toll on artery health while survivors are still children, leaving them vulnerable to premature atherosclerosis and heart disease.

"We may need to start the clock earlier monitoring these children," said Donald Dengel, lead author of the study presented on Sunday at the American Heart Association scientific meeting in Dallas.

"Healthcare providers who are managing chemotherapy-treated childhood cancer survivors need to monitor cardiovascular risk factors immediately following completion of their patients' cancer therapy," said Dengel, a professor at the University of Minnesota.

Researchers used measures of the brachial and carotid arteries to test artery stiffness, thickness and function of 319 Americans ages 9 to 18 who had survived leukemia or other cancers, and compared the findings to 208 siblings not diagnosed with cancer.

Signs of premature heart disease, demonstrated by a decline in artery function, was more prevalent among those children and teenagers who had survived cancer, researchers found.

Childhood leukemia survivors had a 9 percent decrease in arterial health after completing chemotherapy compared with the non-cancer group.

"Given the increased risk, children who survive cancer should make lifestyle changes to lower their cardiovascular risk," Dengel said.

Such changes would include a heart-healthy diet and regular exercise.

However, more studies would be needed to assess whether blood vessel health can be improved by lifestyle changes in these survivors as has been shown in studies of childhood obesity. It may be that damage caused by chemotherapy cannot be reversed, Dengel said.

"I really don't think it's the cancer per se, it's the treatment" that is causing the problems, Dengel added.

A pilot study has begun in which childhood cancer survivors will be given cholesterol lowering statins after puberty to see if that can reduce the risk of future heart problems.

"It may serve them better to be more aggressive," Dengel said.

The study did have limitations, researchers noted.

Because of differences in cancer treatments, they were unable to attribute changes in arterial health to any particular chemotherapy.

In addition, most of the children in the study were white, so the findings were not necessarily applicable to other racial or ethnic groups.

Children in the study, which was funded by the National Institutes of Health and other research groups, had survived at least five years since their initial cancer diagnosis, researchers said.

They said it was the first such study to look at heart health of childhood cancer survivors while they were still children.