Survivors of childhood cancer need to keep a closer watch on their hearts than previously believed, according to new research. Doctors say the harmful cardiac effects of cancer treatments may be more extensive than they realized.

“It’s very important for the general medical community to be aware that this population is at greater risk (for heart problems),” said study co-author Steven Lipshultz, MD, an oncologist and pediatric cardiologist at the University of Rochester Medical Center.

Likewise, survivors need to be sure their doctors know their cancer treatment history so they can monitor them for heart troubles they might not otherwise look for.

Lipshultz and colleagues presented the findings from two studies at last weekend’s annual meeting of the American Society of Clinical Oncology.

Doctors have long known that certain types of cancer therapy – particularly treatment with drugs known as anthracyclines – can cause cardiomyopathy, a weakening of the heart muscle that can lead to congestive heart failure. But these medications are critical to treat certain cancers, so doctors generally recommend that survivors of childhood cancer who received this therapy be monitored over the long term for this particular problem.

What Lipshultz and his colleagues discovered is that many survivors also show other signs of heart disease like atherosclerosis (fatty deposits in the arteries), high cholesterol, and high blood pressure. Doctors typically don’t look for these conditions in this group of patients, Lipshultz said.

In one of their studies, the researchers compared three groups of people: 132 childhood cancer survivors who had received potentially heart-damaging anthracycline chemotherapy or radiation to the heart, 41 survivors who had been treated with other cancer therapies, and 59 siblings of the survivors from both groups who had never had cancer. The survivors had all received their last treatments five or more years before the study.

Lipshultz said the researchers put the study groups through “every test you could think of” for heart conditions; they measured body composition, looked at hormone levels, endocrine levels, heart muscle strength, other muscular function, and more.

They found that patients who had received anthracycline therapy showed an enhanced risk for accelerated atherosclerosis – something that puts them at risk of a heart attack. Even the survivors who did not have heart-damaging therapy showed signs of premature heart disease, Lipshultz said. They had a higher risk than their cancer-free siblings, though not as high as the other group of survivors.

“Basically all survivors of childhood cancer should be screened at some regular set of intervals for risk of atherosclerosis,” Lipshultz said. “If you find it, you can potentially intervene with preventive strategies” like diet and exercise changes, or even medication, he said.

In the second study, Lipshultz and his collaborators examined 48 people who had been successfully treated for Hodgkin disease about 15 years earlier, most when they were teenagers. Almost all of them had been treated with radiation to the chest, including the heart.

None of the patients had any known heart problems, and in health and quality of life questionnaires, all said their overall health was good or better.

But the researchers found that their hearts were not normal. About 60% of the patients had some type of heart valve problems – their valves were “sticky” or leaky. And more than half showed signs that the electrical impulses that control the heart’s beating were slowing down. Lipshultz said some of the survivors also showed evidence of scar tissue in the main pumping chamber of the heart, and narrowing of the arteries with exercise.

“It’s not just a matter of saying if you do enough tests you’ll find something,” Lipshultz said. “Patients who got radiation to the heart (during childhood) really need to be getting regular cardiac screening for all these types of problems.”

Family doctors also need to be aware of these findings, Lipshultz said, because it could affect the way they treat these patients in certain circumstances. A childhood cancer survivor who got these treatments may need to be monitored more closely during pregnancy, for instance, or when starting an exercise regimen.

“If they have a heart impairment, it’s important to know that because they could develop problems,” Lipshultz said.