Prediction of response to immune checkpoint inhibitor therapy using 18F-FDG PET/CT in patients with melanoma

We aimed to assess serial F-18-FDG PET/CT imaging according to morphological (RECIST1.1, iRECIST) and functional (PERCIST, PECRIT) criteria to predict clinical response to therapy in patients with advanced melanoma receiving immune checkpoint blocking agents. Retrospective data collection and analysis was done for 37 patients with unresectable metastatic cutaneous melanoma eligible for immunotherapy (cycles: 4 for ipilimumab and pembrolizumab/6 for nivolumab). F-18-FDG PET/CT imaging was performed prior to (F-18-FDG PET/CT 0) and 14 weeks after ICI onset (F-18-FDG PET/CT 1). Some cases during the follow-up required imaging (F-18-FDG PET/CT 2). Assessment of patient response to treatment was done according to RECIST1.1, iRECIST, PERCIST and PECRIT criteria. Among 37 assessed patients, 27 had 1 line of ICI, 8 had 2 lines of ICI and 2 patients had 3 lines of ICI: total of 49PET/CTs. Mean time between initiation of ICI and F-18-FDG PET/CT (1 or 2) were respectively 13.82 +/- 4.32 and 24.73 +/- 9.53 weeks. Time between F-18-FDG PET/CT 1 and F-18-FDG PET/CT 2 was at mean +/- SD: 11.19w +/- 5.59. Median PFS was 29.62 months (range 22.52-36.71) (P=.001: RECIST 1.1), (P<.0001: iRECIST), (P=.000: PERCIST), (P=.072: PECRIT). Median OS was 36.62 months (30.46-42.78) (P=.005: RECIST 1.1), (P<.0001: iRECIST), (P=.001: PERCIST), (P=.082 PECRIT). F-18-FDG PET/CT could detect eventual ICI-response in patients with metastatic melanoma undergoing ICI using iRECIST and PERCIST criteria.