Background Cardiac magnetic resonance ( CMR) differentiates neoplasm from thrombus via contrast enhancement; positron emission tomography ( PET) assesses metabolism. The relationship between CMR contrast enhancement and metabolism on PET is unknown. Methods and Results The population included 121 cancer patients undergoing CMR and 18F-fluorodeoxyglucose (18F- FDG) - PET , including 66 with cardiac masses and cancer-matched controls. Cardiac mass etiology (neoplasm, thrombus) on CMR was defined by late gadolinium enhancement; PET was read blinded to CMR for diagnostic performance, then colocalized to measure FDG avidity. Of CMR -evidenced thrombi (all nonenhancing), none were detected by PET . For neoplasm, PET yielded reasonable sensitivity (70-83%) and specificity (75-88%). Lesions undetected by PET were more likely to be highly mobile ( P=0.001) despite similar size ( P=0.33). Among nonmobile neoplasms, PET sensitivity varied in relation to extent of CMR -evidenced avascularity; detection of diffusely enhancing or mixed lesions was higher versus predominantly avascular neoplasms (87% versus 63%). Colocalized analyses demonstrated 2- to 4-fold higher FDG uptake in neoplasm versus thrombus ( P<0.001); FDG uptake decreased stepwise when neoplasms were partitioned based on extent of avascularity on late gadolinium enhancement CMR ( P≤0.001). Among patients with neoplasm, signal-to-noise ratio on late gadolinium enhancement CMR moderately correlated with standardized uptake values on PET ( r=0.42-0.49, P<0.05). Mortality was higher among patients with CMR -evidenced neoplasm versus controls (hazard ratio: 1.99 [95% CI, 1.1-3.6]; P=0.03) despite nonsignificant differences when partitioned via FDG avidity (hazard ratio: 1.56 [95% CI, 0.85-2.74]; P=0.16). Among FDG-positive neoplasms detected concordantly with CMR , mortality risk versus cancer-matched controls was equivalently increased (hazard ratio: 2.12 [95% CI, 1.01-4.44]; P=0.047). Conclusions CMR contrast enhancement provides a criterion for neoplasm that parallels FDG -evidenced metabolic activity and stratifies prognosis. Extent of tissue avascularity on late gadolinium enhancement CMR affects cardiac mass identification by FDG - PET .
Keywords: cardiac magnetic resonance; cardiac neoplasm; cardio‐oncology; positron emission tomography.