Outcome prediction based on [18F]FDG PET/CT in patients with pleural mesothelioma treated with ipilimumab and nivolumab +/- UV1 telomerase vaccine

Abstract

Purpose The introduction of immunotherapy in pleural mesothelioma (PM) has highlighted the need for efective outcome predictors. This study explores the role of [18F]FDG PET/CT in predicting outcomes in PM treated with immunotherapy. Methods Patients from the NIPU trial, receiving ipilimumab and nivolumab +/- telomerase vaccine in second-line, were included. [18F]FDG PET/CT was obtained at baseline (n = 100) and at week-5 (n = 76). Metabolic tumour volume (MTV) and peak standardised uptake value (SUVpeak) were evaluated in relation to survival outcomes. Wilcoxon rank-sum test was used to assess diferences in MTV, total lesion glycolysis (TLG), maximum standardised uptake value (SUVmax) and SUVpeak between patients exhibiting an objective response, defned as either partial response or complete response according to the modifed Response Criteria in Solid Tumours (mRECIST) and immune RECIST (iRECIST), and non-responders, defned as either stable disease or progressive disease as their best overall response. Results Univariate Cox regression revealed signifcant associations of MTV with OS (HR 1.36, CI: 1.14, 1.62, p < 0.001) and PFS (HR 1.18, CI: 1.03, 1.34, p = 0.02), while multivariate analysis showed a signifcant association with OS only (HR 1.35, CI: 1.09, 1.68, p = 0.007). While SUVpeak was not signifcantly associated with OS or PFS in univariate analyses, it was signifcantly associated with OS in multivariate analysis (HR 0.43, CI: 0.23, 0.80, p = 0.008). Objective responders had signifcant reductions in TLG, SUVmax and SUVpeak at week-5. Conclusion MTV provides prognostic value in PM treated with immunotherapy. High SUVpeak was not associated with inferior outcomes, which could be attributed to the distinct mechanisms of immunotherapy. Early reductions in PET metrics correlated with treatment response.