Radiation Heart Disease: A Few Learnings on a Diverse, Daunting Entity

The overlap between cancer and heart disease in recent years has been a mix of bad and good news. On one hand, cancer diagnoses are on the rise. On the other hand, improved cancer therapies are resulting in the largest cohort of cancer survivors we’ve ever seen. At the same time, those survivors often face a secondary battle 15 to 25 years later in the form of radiation-associated heart disease.

The heart as collateral damage

“Radiation therapy for some forms of cancer involves a large dose of radiation to the chest,” says Milind Desai, MD, Director of Cardiovascular Imaging Research at Cleveland Clinic. “The heart can suffer collateral damage as a result.”

Although improved radiation therapy techniques enable reduced dosage and volume of radiation exposure, radiation-treated cancer survivors remain at increased risk of cardiovascular diseases. These patients are increasingly presenting with complicated cases of coronary artery disease, valve disease, cardiomyopathy and lung fibrosis. “There is not one unique entity,” Dr. Desai says. “It can cover the spectrum of cardiovascular disease.”

The one thing most cases have in common is that they require individualized care at an experienced multidisciplinary center of excellence, he adds.

Close follow-up is imperative

While it’s important for patients to make their cardiovascular providers aware of past radiation treatments, it’s just as important for providers to adopt a multidisciplinary approach that begins with close clinical follow-up of cancer survivors. Dr. Desai recommends a management strategy that involves multiple screening modalities, including echocardiography to look for peculiar patterns, ischemic evaluation, pulmonary function tests and pulmonary evaluation.

A noncontrast CT of the ascending aorta (porecelain aorta) in a 58-year-old woman with a history of radiation-associated heart disease.

“Because everybody is different and the extent of radiation therapy varies among patients, it’s important to understand the full spectrum,” he says. “These patients do not just have a coronary artery problem or a valve problem or a lung problem. A given individual may have everything wrong, or everything wrong in moderation.”

Guideposts for identification

The key to identifying true radiation-associated heart disease, says Dr. Desai, is later injury — whether constrictive pericarditis, coronary artery disease, valvular disease or conduction abnormalities. He adds that the prevalence of radiation-associated heart disease is difficult to ascertain, due in part to its considerable latency, although it appears to be increasing.

Risk factors for radiation-associated heart disease include:

• Total radiation dose > 20-35 Gy
• Doses > 2 Gy/day
• Increased volume of heart irradiated
• Younger age
• Time since exposure
• Concomitant cardiotoxic chemotherapy
• Other cardiovascular risk factors (diabetes mellitus, smoking)
• Radiation source (cobalt)

Management: Surgery often needed, but more risky

“A lot of these patients will end up needing heart surgery because of the damage to their heart,” Dr. Desai says, but he notes that their surgical outcomes are typically worse than for other heart surgery patients.

Consider an observational study he and his colleagues published in Circulation a few years ago. It demonstrated that patients undergoing cardiothoracic surgery at Cleveland Clinic over a three-year period had a 2.5-fold elevated mortality risk if they had a history of malignancy requiring chest irradiation compared with matched controls who underwent the same surgery but did not have a history of malignancy or chest irradiation. Most of the patients with the cancer history had had either breast cancer (53 percent) or Hodgkin lymphoma (27 percent).

In light of outcomes like these, Dr. Desai recommends judicious use of surgical intervention in cases of radiation-associated heart disease. Alternative treatment approaches, including transcatheter aortic valve replacement or other percutaneous interventions, may be more appropriate after identifying risk. That argues all the more, he notes, for management at a versatile center of excellence with broad diagnostic and therapeutic offerings and a deep experience base.