Immune Checkpoint Inhibitor Myocarditis on FDG PET/CT and Cardiac MR.

A patient with stage 4 squamous cell carcinoma treated with pembrolizumab developed heart failure symptoms attributed to immune checkpoint inhibitor-related myocarditis.

• The patient was a 54-year-old man.
• He had stage 4 squamous cell carcinoma and was receiving pembrolizumab.
• He presented with symptoms of heart failure.

FDG PET/CT showed new cardiomegaly with intense myocardial FDG uptake at the time of presentation.

• Cardiomegaly was new compared with prior imaging.
• Myocardial tracer uptake was described as intense.
• This is a single case report, so no group statistics are given.

Concurrent contrast-enhanced cardiac MRI demonstrated myocardial edema and gadolinium enhancement consistent with myocarditis.

• The MRI was performed concurrently with the FDG PET/CT.
• Findings were myocardial edema and gadolinium enhancement.
• These findings were consistent with a diagnosis of myocarditis.

Follow-up FDG PET/CT after stopping immunotherapy and starting prednisolone showed resolution of cardiomegaly and abnormal myocardial tracer uptake, supporting the specific etiology.

• Immunotherapy was ceased and prednisolone was initiated.
• Repeat FDG PET/CT showed resolution of both cardiomegaly and abnormal myocardial uptake.
• The authors state this resolution further substantiated the specific etiology of the myocarditis.

Immune checkpoint inhibitor-related myocarditis is a rare immune-related adverse effect with disproportionately high mortality.

• This is stated as background in the abstract.
• It frames the clinical relevance of the imaging findings in the case.