The Prospective Assessment Of Rt-Associated Changes In Myocardial Perfusion And Function In Patients Irradiated For Thoracic Malignancies

Cardiac irradiation can increase cardiac events years post-RT. Sub-clinical changes in cardiac perfusion, of unclear significance, can be seen within mos of RT in breast cancer patients. We herein report the incidence of early changes in cardiac perfusion in patients with other thoracic tumors. Between 2006-7, 20 pts were enrolled on an IRB-approved prospective clinical trial to monitor post-RT cardiac events. Patients with ≥5% of the left ventricle (LV) receiving ≥20 Gy underwent pre- and serial post-RT (3, 6, 12, and 18 mo) single photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) cardiac scans. Changes in cardiac perfusion, wall motion, and ejection fraction (EF) were scored by a nuclear cardiologist/radiologist, blinded to clinical factors. Subgroups were defined based on the percent of heart/LV receiving varying doses of RT and results were compared using two-tailed Fisher's exact tests. Of the 20 enrolled patients, 19 patients had pre-RT SPECT scans, and 3, 10, 3, and 1 patient had post-RT scans at 3, 6, 12, and 18 months, respectively. Patient characteristics: median age 62 yrs (range, 40-79 yrs); lung cancer 70%, mesothelioma 25%, and other 5%; and race 85% Caucasian, 15% African American. The overall rate of worsening perfusion measured by an increase in SRS was 50% in the 12 patients with post-RT scans. The rates of new perfusion defects were 33% (1/3), 30% (3/10), 33% (1/3), and 0 (0/1) at 3, 6, 12, and 18 months post-RT, respectively. Of those patients who experienced worsening perfusion defects, new regions of wall motion abnormalities were seen in 75% (6/8) of follow-up scans. Two patients experienced a >20% reduction in EF 6 mos post-RT. The average reduction in ejection fraction was 3%, 4%, 7%, and 11% at 3, 6, 12, and 18 mos, respectively as assessed by SPECT. Mean heart dose did not predict for perfusion defects, with rates of new defects 4/6 and 1/6 in patients with a mean heart dose < vs. > the population median of 23 Gy (p = 0.34). The MRI scans typically did not demonstrate any significant changes. One patient with a known pre-existing heart condition was hospitalized for tachycardia 6 mos post-RT. No other clinically related cardiac symptoms were observed. New RT-induced perfusion defects occur in approximately 50% of patients who have ≥5% of their left ventricle receiving ≥20 Gy. Additional follow-up of larger patient numbers is needed to clarify the impact of RT on the development of perfusion defects, the longevity of these defects, and their clinical implications.