(The Associated Press) -- Children who survive cancer face a much greater risk of heart problems later in life than their brothers and sisters who did not have cancer, new research shows.

Doctors have long known that certain chemotherapy drugs and radiation can harm the heart, but it has been seen as a relatively small price to pay for beating cancer. Cancer itself may damage the heart. And even though the risk was higher, heart problems still were relatively rare.

The study used a national registry to track 14,358 cancer survivors diagnosed in the 1970s and 1980s, when treatments were harsher than those commonly used today, and compared them to about 4,000 healthy siblings.

The survivors had one of eight forms of the disease, including leukemia, brain tumors, Hodgkin's or non-Hodgkin's lymphoma and kidney tumors.

Compared to their healthy siblings, they had five to 10 times greater risk of heart problems, ranging from clogged arteries to heart failure and valve disease.

The risk often showed up when they were still young adults -- an age when few doctors would think to check them for heart problems. The survivors were diagnosed with cancer at an average age of 8, and their average age was 28 when the follow-up study was done.

There are about 270,000 childhood cancer survivors in the United States today, said the study's leader, Dr. Daniel Mulrooney at the University of Minnesota.

"They have to live with the health consequences of having had cancer and having been treated for cancer," he said.

Still, the incidence of problems was low: 2 percent had hardening of the arteries, 4 percent had heart failure, 1 percent suffered a heart attack and 4 percent had a valve problem.

Study results were released Thursday by the American Society of Clinical Oncology and will be presented at the group's annual meeting later this month.

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