Child cancer survivors face heart risks

Children and teens who survive cancer show a significantly higher risk of developing heart disease as young adults compared with their siblings, a study suggests.

Researchers found young adult survivors of childhood cancer were at risk for complications related to their cancer therapy, including heart attacks, heart failure, inflammation of the heart and heart valve problems, up to 30 years after treatment.

"Young adults who survive childhood or adolescent cancer are clearly at risk for early cardiac morbidity and mortality not typically recognized within this age group," said Dr. Daniel Mulrooney, a pediatric hematology oncologist from the University of Minnesota.

"Such individuals require ongoing clinical monitoring, particularly as they approach ages in which cardiovascular disease becomes more prevalent," he and his colleagues concluded.

For the study, researchers compared data on more than 14,350 five-year cancer survivors, including Canadians, who took part in a childhood cancer survivor study and about 3,900 siblings of survivors.

Before age 21, all of the cancer survivors studied had been diagnosed with either leukemia, brain cancer, Hodgkin's lymphoma, non-Hodgkin's lymphoma, kidney cancer, neuroblastoma, soft tissue sarcoma, or bone cancer between 1970 and 1986.

Survivors were 5.9 times more likely to report congestive heart failure and five times more likely to report heart attacks compared with their siblings, the team found.

Those who had been treated with chemotherapy had a two to five times higher risk than those who had no chemotherapy. Radiation exposure also increased the risk by two to six times compared with those who had not had radiotherapy.

Collaborate on surveillance

In 80 per cent of the patients exposed to one chemotherapy agent, known as anthracyclines, the cardiac damage was not clinically significant, but treatment will often be started with the aim of conserving function, Meriel Jenney, a pediatric oncologist from the Children’s Hospital for Wales in Cardiff  said in a journal commentary.

The study raises questions about surveillance levels, with current heart screening guidelines varying from routine heart screening every five years in Britain to more frequently in the United States and Canada for those considered to be at higher risk.

The North American guidelines depend on age at treatment, whether the patient received radiation therapy to the chest, and the dose of anthracyclines, said Dr. Paul Nathan, a staff oncologist at the Hospital for Sick Children in Toronto. The recommended screenings range from one to five years, depending on this combination of factors.

"It is possible that too many patients are subjected to long term hospital follow-up, with unnecessary costs to healthcare systems, but it is hard to ignore the few for whom this could be important," Jenney wrote.

"With the number of adult survivors steadily rising, a cost effective approach may be for children's services that assess late effects to merge with adult services that provide a network of specialists with expertise in this area. It makes sense to collaborate across age boundaries to optimize the care pathways for these patients with complex problems."

The findings are important not only for cancer specialists, but also for cancer survivors and family physicians, Nathan said.

For example, Ontario has five clinics designed for child cancer survivors, but many of them may not be aware of the clinics and go to their family doctors for follow-ups instead. Or a heart attack may occur in a childhood cancer survivor at an earlier age than family doctors and emergency room physicians expect.

Oncologists still don't know much about what the best interval for screening is for child cancer survivors, or who doesn't need it, since relatively fewer people are affected compared with other screening programs, such as mammography. 

Overall, cardiac screening using ultrasounds of the heart is not that expensive, Nathan said. The smaller population of child cancer survivors also means that Canadians may be willing to spend more on screening them, which he called a valid point for discussion.