ASTRO Patient Summary: Objective Versus Subjective Assessment of Single Photon Emission Computed Tomography (SPECT) Cardiac Perfusion Scans to Assess for Radiation Therapy (RT) Induced Cardiac Injury
It has long been known that women who receive radiation to the left breast have portions of heart tissue exposed to radiation, and can develop cardiac complications as a result. Although newer radiation techniques result in less damage, some still does occur. This study looked at how to evaluate that damage. The study used a scan called Single Photon Emission Computed Tomography (or SPECT) to evaluate heart damage. This scan uses a radiolabeled tracer, which is administered to the patient and then picked up by a CT scan. The test evaluates blood flow to organs, in this case, the heart. The study found that the amount of damage correlates with the amount of heart tissue in the field of radiation. About 30% of the patients with <1% of the heart muscle in the radiation field developed damage seen on SPECT, while >90% of the patients with >10% of heart muscle in the radiation field developed damage seen on SPECT. The next issue is whether patients with damage seen on SPECT actually develop cardiac problems. Unfortunately, we do not know what the long-term significance is of this damage. These patients should be followed closely to determine if abnormalities on SPECT are a way to predict who might develop cardiac complications, allowing them to be more closely monitored.