Cardiovascular complications of radiation therapy for thoracic malignancies: the role for non-invasive imaging for detection of cardiovascular disease

Abstract

Radiation exposure to the thorax is associated with substantial risk for the subsequent development of cardiovascular disease. Thus, the increasing role of radiation therapy in the contemporary treatment of cancer, combined with improving survival rates of patients undergoing this therapy, contributes to a growing population at risk of cardiovascular morbidity and mortality. Associated cardiovascular injuries include pericardial disease, coronary artery disease, valvular disease, conduction disease, cardiomyopathy, and medium and large vessel vasculopathy-any of which can occur at varying intervals following irradiation. Higher radiation doses, younger age at the time of irradiation, longer intervals from the time of radiation, and coexisting cardiovascular risk factors all predispose to these injuries. The true incidence of radiation-related cardiovascular disease remains uncertain due to lack of large multicentre studies with a sufficient duration of cardiovascular follow-up. There are currently no consensus guidelines available to inform the optimal approach to cardiovascular surveillance of recipients of thoracic radiation. Therefore, we review the cardiovascular consequences of radiation therapy and focus on the potential role of non-invasive cardiovascular imaging in the assessment and management of radiation-related cardiovascular disease. In doing so, we highlight characteristics that can be used to identify individuals at risk for developing post-radiation cardiovascular disease and propose an imaging-based algorithm for their clinical surveillance.

Keywords: Non-invasive imaging; Radiation therapy.

Figure 1

Classification of cardiovascular injury following radiation therapy.

Figure 2

Non-invasive imaging can aid in the assessment of cardiovascular complications following radiotherapy, as shown in the following examples: (A) pericardial thickening on a T2-weighted cardiac MR in a 52-year-old male found to have constrictive pericarditis 18 years following mediastinal irradiation; (B) circumferential late gadolinium enhancement of the thickened pericardium on cardiac MR in the same patient; (C) pericardial calcification seen by non-contrast CT imaging in a patient with a remote history of thoracic irradiation; (D) respiratory variation in mitral inflow peak E-wave velocities and rapid deceleration time, seen via pulse-wave Doppler echocardiography in a patient with constrictive pericarditis following radiation therapy; (E) respiratory variation in hepatic vein pulse-wave Doppler signal in the same patient as in part D; (F) diffuse calcification of the thoracic aorta on contrast-enhanced CT in another patient who received Mantle radiotherapy in childhood; (G) extensive calcification of the aortic valve on contrast-enhanced CT in a patient imaged 10 years after thoracic radiation; (H) stress and rest N¹³-ammonia PET perfusion in a 58-year-old female 8 years post-mediastinal radiation, demonstrating a medium-sized perfusion defect of moderate intensity in the mid-anteroseptal, mid-inferoseptal walls, the apical septum, apical inferior wall and apex that was partly reversible, consistent with ischaemia in the distribution of the mid-left anterior descending artery. In addition, there was a medium-sized defect of moderate intensity in the entire inferolateral wall that was reversible, consistent with ischaemia in the distribution of an obtuse marginal artery.

Figure 3

A proposed clinical algorithm for screening and diagnosis of radiation-induced cardiovascular disease. *Choice of functional imaging modality to be guided by local availability and expertise.