18F-FDG-PET/CT response assessment in patients with advanced melanoma treated with combination of low-dose ipilimumab and anti-PD1: A real-world experience.

Abstract

e21533 Background: Combination therapy with anti-PD1 and low-dose ipilimumab has shown reduced rate of immune-related adverse effects compared with standard dose used in the Checkmates studies 067 and 204. However, the discussion whether low-dose ipilimumab may hamper the response rate in advanced melanoma is still open. Methods: We conducted a retrospective analysis of response evaluation based on 18F-FDG PET/CT for patients with advanced melanoma treated with combination of nivolumab 3mg/kg plus ipilimumab 1mg/kg for 4 cycles (N3+I1) followed by anti-PD1 maintenance therapy and compared the results to RECIST 1.1 response criteria in the same population. Results: Between December 2017 and August 2020, 45 patients with advanced melanoma treated with N3+I1 in first-line setting were identified. Unresectable stage III/stage IV were 2/43 patients, respectively. Among stage IV patients, 60.5% were M1c, 23.3% had elevated LDH and 28% had brain metastasis (3 or more brain lesions: 58%). At a median follow-up of 16.7 months, 11 patients (24.4%) had G3/G4 toxicity. During induction phase, three patients (6.6%) discontinued all drugs and 2 other patients (4.4%) interrupted only ipilimumab. Review of response evaluation by RECIST was possible in 36 patients and showed an objective response of 50%. Complete response (CR): 11% and partial response (PR): 39%. Eight percent presented progressive disease (PD). In 37 patients, review of response evaluation using 18F-FDG PET/CT was possible. Twenty-four patients (65%) achieved metabolic CR, 5 (13.5%) PD and 8 (21.5%) were classified as non-CR non-PD. Median progression-free survival (PFS) and overall survival(OS) were not reached. 12-month PFS and OS were: 72.5 and 89%, respectively. During the study follow-up, only 1 patient with metabolic complete response relapsed and 3 out of 8 with non-CR non-PD progressed. Conclusions: Using low-dose ipilimumab combination does not hamper the response rates and, possibly due to fewer protocol interruptions, these patients may achieve more complete responses as showed by 18F-FDG PET/CT evaluation.