Our success at treating children with cancer has steadily improved in the 40 years since President Nixon announced the War on Cancer. At the time, 3 in 10 children survived a diagnosis of cancer; now upwards of 8 in 10 do. The U.S. alone is home to an estimated 328,000 childhood cancer survivors today.
But as these survivors age, they can experience late effects, long-term medical complications of the very treatments that saved their lives. In fact, 30 years out, survivors are at more risk of dying from treatment-related illness than from cancer recurrence.
Perhaps the most insidious late effect – and the leading cause of non-cancer death at the 30-year mark – is cardiovascular disease.
Treatment-related heart damage can take decades to appear. This long latency means that a woman treated for cancer at age 6 could face a heart attack when she’s 36. And she might never see it coming. “A survivor can walk around for years with minimal symptoms while their cardiovascular disease silently progresses,” says Ming Hui Chen, an adult cardiologist at Children’s Hospital Boston.
Chen and her colleagues Steven Colan, also of Children’s Department of Cardiology, and Lisa Diller, of the Children’s Division of Hematology/Oncology and the Dana Farber/Children’s Hospital Cancer Center, reviewed the state of knowledge on late cardiovascular effects in childhood cancer survivors in a recent article in Circulation Research. They argued for tailoring modern cancer therapy to meet both the present and future needs of the patient.
Essentially, the severity of the late effects is closely tied to four factors: the amount of radiation received, the size and shape of the radiation field, the type of chemotherapy (e.g., anthracyclines) or radiation therapy received, and how long ago the patient was in treatment.
Cardiovascular disease can be of particular concern for survivors of Hodgkin’s lymphoma. The standard regimen for this cancer includes radiation to the chest, which can thin and stiffen the walls of the heart (which would lie within the radiation field), limiting the heart’s ability to contract and relax. Meanwhile, radiation’s damaging effects on the nerves of the chest mute the typical warning signs – chest pain or tightness – of impending heart trouble.
Given its silent nature, it is vital that survivors of Hodgkin’s lymphoma and other childhood cancers be routinely screened for cardiovascular disease. Unfortunately, many of the common screening techniques, such as coronary angiography and nuclear perfusion, are invasive or require additional radiation exposure, something survivors should avoid if they can.
Chen is trying to circumvent these limitations by screening survivors using exercise stress echocardiography (ESE). This non-invasive technique, more often used in adults, has been offered at Children’s since 2006 through the Pediatric Exercise Stress Echocardiography Program.
An ESE test captures ultrasound images of a survivor’s heart at rest and just after a short jog on the treadmill. It lets doctors assess a patient’s exercise capacity – an important predictor of cardiac health. “We’re looking at our patients’ hearts while they exercise to see how much reserve they have,” Chen explains, “and how much of that reserve cancer therapy has taken away.”
Chen and colleagues in the Cardiomyopathy and Heart Failure programs are following a large cohort of cancer survivors with routine cardiac care and screening, even if they are not yet experiencing outward signs or symptoms of cardiovascular disease. With her oncology colleagues at Dana-Farber Cancer Institute and Brigham and Women’s Hospital, Chen is also conducting a three-year study to identify cardiovascular disease risk factors in cancer survivors.
“A better understanding of the modifiable cardiac risk factors can help doctors identify survivors who, even though they may appear well, are likely to be at high risk of developing heart disease,” she says.
Despite their long-term effects, chemotherapy and radiation therapy remain very effective, life-saving cancer treatments and, Chen and her colleagues believe, will remain the standard of care for a long time to come. Which means that routine cardiac screening is crucial for long-term health.
“That’s why our clinic starts with childhood survivors when they are well, even when they show no signs of cardiac problems,” Chen says. “Through research and clinical care, we could, if not prevent, maybe forestall these problems. For any survivor, that would be significant.”