Low/slow accrual (change in standard treatment practice)

The purpose of this pilot study is to evaluate Fluorodeoxyglucose - Positron Emission Tomography (FDG-PET) as an imaging modality to diagnose and risk stratify subclinical, imaging negative ICI-myocarditis, and to determine whether subclinical ICI-induced myocarditis is a distinct and clinically relevant entity with a risk of progression to fulminant myocarditis.

Inclusion Criteria:

• Age ≥18 years at the time of signing informed consent
• Any solid or hematologic malignancy undergoing treatment with ICI (either as a single agent or in combination with others)
• Ambulatory and able to complete a 48-72 hour high fat and low carbohydrate diet with 18 hours fasting (PET diet), 18F-FDG PET/CT scanning, as well as 13N-ammonia PET-CT myocardial perfusion imaging (part of the routine protocol of the investigation). These two studies will be done as part of the same imaging set.
• Willing to return to Mayo Clinic for ongoing follow-up
• Left ventricular ejection fraction (LVEF) ≥45%
• Cardiac MRI (CMR) without conclusive evidence of inflammation, coronary assessment available (either via cardiac computed tomography angiography, CCTA, or via coronary angiogram) Informed consent obtained before any trial-related activities. Trial-related activities are any procedures that are carried out as part of the trial, including activities to determine suitability for the trial.

Exclusion Criteria:

• Fulminant myocarditis requiring steroid therapy
• CMR with definitive evidence of myocarditis
• Clinical presentation consistent with acute coronary syndrome (wall motion abnormalities consistent with a specific coronary distribution, coronary angiogram with a culprit lesion identified, patients requiring revascularization either with percutaneous coronary interventions or coronary artery bypass grafting).
• Patients unable to provide informed consent
• Patients unable to complete the diet preparation protocol
• Pregnancy (all women of child-bearing age and potential will have a negative pregnancy test within 48 hours of the PET/CT at screen and 6-month visit)
• Breastfeeding

Adult male or female patients diagnosed with having a solid tumor or cancers in the blood and who are undergoing treatment with immune checkpoint inhibitors (ICI) either as a single agent or in combination with others.