SUNDAY, July 3, 2005 (HealthDay News) -- Many survivors of childhood cancer end up with hearts that are too small for their bodies. As adults, this can translate into heart failure, transplant waiting lists, and even death.
A new study of these survivors has found, almost by accident, that growth hormone therapy resulted in larger hearts that were more in line with their body size.
"This was a safe therapy, and it brought them closer to normal," said Dr. Steven Lipshultz, lead author of the study, which appears in the June issue of Pediatrics.
"It's a very important tool," added Dr. Revathy Sundaram, a pediatric oncologist at Long Island College Hospital in New York City. "All of us should start looking into using this or at least discuss it."
The findings have implications not only for childhood cancer survivors, but also for other children with hearts that are too small.
"The No. 1 problem that causes children around the world to need a heart transplant is cardiomyopathy or unhealthy heart muscle," explained Lipshultz, a professor and chairman of pediatrics at the University of Miami School of Medicine. "One of the main causes of cardiomyopathy is the inability of the heart muscle to keep up with the size of the body. They are basically outgrowing their heart."
And one reason for the inability of the heart muscle to keep up with the body's growth is when anthracycline chemotherapy drugs are administered to children with leukemia.
"The chemotherapy they received kept them alive, but it wasn't specific for cancer cells. A number of heart muscles were killed as well," Lipshultz said. "These long-term survivors have an eightfold higher risk of dying of cardiac death than if they had never been treated, and it just keeps getting worse when they get older."
Chemotherapy and radiation can also damage regions of the brain that make growth hormone, Lipshultz explained.
Perhaps 25 percent to 30 percent of children treated with these drugs end up with small hearts, Sundaram said. "Then the blood vessels within the heart are small so now you have an adult with a small heart and you might get blocking of the blood vessels, so you're at risk for heart problems," she said.
To date, the main "solution" has been to monitor these individuals closely. There have been almost no randomized, controlled trials because it's so difficult to get to the endpoints of whether the child is going to live or not, Lipshultz explained.
The children in this study actually received growth hormone not because of heart problems, but because they were shorter than other children their age. When they reached an appropriate height, doctors stopped the administration of growth hormone.
But there was an unanticipated and very welcome "side effect."
Thirty-four childhood cancer survivors treated with anthracyclines for their cancer and later with growth hormone saw a normalization of the wall thickness of the heart's left ventricle (the main pumping chamber), as well as heart rate and blood pressure.
These measures returned to previous levels when the hormone therapy was stopped -- which it was when children reached a more-or-less normal height.
"For these children that don't have enough heart muscle for the size of their body and wind up dying at much higher rates prematurely of heart disease and have much higher rates of needing heart transplants, giving injections of growth hormones resulted in making more muscle, as long as you keep the growth hormone up," Lipshultz said.
Administration of growth hormone could be kept up indefinitely, Lipshultz added.
Dr. Jay Brooks, chairman of hematology/oncology at the Ochsner Clinic Foundation in New Orleans, said, "This is a very good study. But this is a highly selected group of children . . . I think now this will probably become an important part of treatment in this group. This should not mean that all kids should be getting growth hormone."
The Candlelighters' Childhood Cancer Foundation has more on chemotherapy's effect on the heart.