Immune-mediated Disease in Ipilimumab Immunotherapy of Melanoma with FDG PET-CT.

RATIONALE AND OBJECTIVES: The purposes of this study were to provide a case-based overview of various immune-mediated side effects detected by 18F-Fluorodeoxyglucose (F-18 FDG) positron emission tomography-computed tomography (PET-CT) in the patients receiving ipilimumab immunotherapy for treatment of malignant melanoma, and discuss the importance of recognizing immune-mediated side effects in the use of F-18 FDG PET-CT for monitoring therapeutic effects of ipilimumab on metastatic melanoma.

MATERIALS AND METHODS: This is a retrospective case series study of the patients diagnosed with melanoma who were subjected to immunomodulating therapy with ipilimumab. F-18 FDG PET-CT findings were reviewed, and the patients with immune-mediated side effects were selected for further analysis, in conjunction with review of clinical progress notes, the results of laboratory tests, and findings of other imaging tests.

RESULTS: Four patients with immune-mediated side effects were identified among the patients being treated with ipilimumab and subjected to F-18 FDG PET-CT for monitoring therapeutic effects. These immune mediated side effects include new findings of abnormal increased FDG uptake associated with immune-mediated pancreatitis and hypophysitis, as well as immune-mediated thyroiditis and colitis reported previously.

CONCLUSIONS: Various immune-mediated side effects were detected by F-18 FDG PET-CT in the patients subjected to immunomodulating therapy with ipilimumab. It is essential for the interpreting provider to recognize and differentiate abnormal FDG uptake associated with immune-mediated side effects from hypermetabolic malignant lesions when using F-18 FDG PET-CT for monitoring therapeutic effects of ipilimumab on melanoma lesions.