Scintigraphic Techniques for Early Detection of Cancer Treatment-Induced Cardiotoxicity

New antitumor agents have resulted in significant survival benefits for cancer patients. However, several agents may have serious cardiovascular side effects. Left ventricular ejection fraction measurement by Tc-99m multigated radionuclide angiography is regarded as the gold standard to measure cardiotoxicity in adult patients. It identifies left ventricular dysfunction with high reproducibility and low interobserver variability. A decrease in left ventricular ejection fraction, however, is a relatively late manifestation of myocardial damage. Nuclear cardiologic techniques that visualize pathophysiologic processes at the tissue level could detect myocardial injury at an earlier stage. These techniques may give the opportunity for timely intervention to prevent further damage and could provide insights into the mechanisms and pathophysiology of cardiotoxicity caused by anticancer agents. This review provides an overview of past, current, and promising newly developed radiopharmaceuticals and describes the role and recent advances of scintigraphic techniques to measure cardiotoxicity. Both first-order functional imaging techniques (visualizing mechanical [pump] function), such as Tc-99m multigated radionuclide angiography and Tc-99m gated blood-pool SPECT, and third-order functional imaging techniques (visualizing pathophysiologic and neurophysiologic processes at the tissue level) are discussed. Third-order functional imaging techniques comprise I-123-metaiodobenzylguanidine scintigraphy, which images the efferent sympathetic nervous innervations; sympathetic neuronal PET, with its wide range of tracers; In-111-antimyosin, which is a specific marker for myocardial cell injury and necrosis; Tc-99m-annexin V scintigraphy, which visualizes apoptosis and cell death; fatty-acid-use scintigraphy, which visualizes the storage of free fatty acids in the lipid pool of the cytosol (which can be impaired by cardiotoxic agents); and In-111-trastuzumab imaging, to study trastuzumab targeting to the myocardium. To define the prognostic importance and clinical value of each of these functional imaging techniques, prospective clinical trials are warranted.