Association of myocardial uptake on early FDG PET with cardiac radiation dose and cardiotoxicity after concurrent chemoradiotherapy for lung cancer

1674 Purpose: Myocardial FDG uptake is considered to increase after radiation therapy in a dose-dependent manner. However, its associations with future cardiotoxicity remains unclear, particularly for FDG PET performed early after radiation therapy. We analyzed the FDG PET images performed early after concurrent chemoradiotherapy (CCRT) for lung cancer to clarify this issue. Methods: We retrospectively identified patients with stage III non-small cell lung cancer, who underwent CCRT and restaging FDG PET within 1 month (median 11 days). Among them, those who survived at least 6 months were finally included. For the evaluation of dose-uptake relationships, FDG uptake was measured for the total left ventricle (LV) myocardium, LV myocardium irradiated ≥5 Gy, and LV myocardium irradiated <5 Gy. The standardized uptake value (SUV) was compared between myocardium irradiated ≥5 Gy vs. <5 Gy for eligible patients. The development of cardiotoxicity (≥grade 2 cardiac event defined by the Common Terminology Criteria for Adverse Events version 4.03) was investigated and its association with myocardial FDG uptake was evaluated. Results: The final analyses included 111 patients. Sixty-nine among them had myocardium irradiated ≥5 Gy and were eligible for dose-uptake comparison. LV myocardium irradiated ≥5 Gy showed significantly higher maximal (8.05 vs. 6.70; p = 0.005) and mean (4.28 vs. 3.62; p 1.02 showed significantly higher incidence of cardiotoxicity, it could not independently predict cardiotoxicity while V5 >17.12 cm3 could. Conclusions: On early FDG PET after CCRT, FDG uptake was higher in LV myocardium irradiated ≥5 Gy. Higher uptake in LV myocardium irradiated ≥5 Gy was observed in patients with future cardiotoxicity. However, it was not independently predictive of cardiotoxicity development.