Late Gadolinium Enhancement Cardiac Magnetic Resonance Tissue Characterization for Cancer-Associated Cardiac Masses: Metabolic and Prognostic Manifestations in Relation to Whole-Body Positron Emission Tomography

Abstract

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.