92 Chapter 5 Figure 4 Example fused images of [89Zr]Zr-DFO-durvalumab (10mg) PET/CT images showing tracer uptake in known tumor locations Displaying transversal sections in 4 different patients. The white arrows highlight tumor lesions in lung (A), local recurrence (B), lymph node and pleural lesion (C) and two other bone lesions (D) The largest heterogeneity in one patient was observed between a lung (SUVpeak 3.3) and liver (SUVpeak 9.8) metastasis. Highest SUVpeak values were reported in two bone lesions (SUVpeak 13.4 and SUVpeak 13.6) and one locoregional lymph node (SUVpeak 12.2). [ 89Zr]Zr-DFO-durvalumab SUVpeak was correlated with lesion size (Spearman ρ 0.359, p= 0.09) and [ 18F]FDG SUVpeak (Spearman ρ 0.391, p=0.005), but not with organ site (Spearman ρ 0.15, p= 0.28). The overall mean gm [89Zr]Zr-DFO-durvalumab SUVpeak was 6.0 (95%CI 4.6-7.3). [18F]FDG PET imaging. In 33 patients, 70 [18F]FDG -positive lesions were identified according to PERCIST criteria used for quantitative analyses. The [18F]FDG uptake was highly variable within and between patients, with overall gm [18F]FDG SUVpeak 7.7 (range 2.0-18.2) and [ 18F]FDG TLG 70.3 ml (range 2.7-659.0 ml). Correlation between tracer uptake and treatment response or PD-L1 expression [89Zr]Zr-DFO-durvalumab PET/CT The median PFS of patients with an above median [89Zr]Zr-DFO-durvalumab SUVpeak was 5.7 months compared to 3.5 months in the below median group (HR 1.5 (95%CI 0.5-3.9, p=0.45, Figure 5A). Also, gm [89Zr]Zr-DFO-durvalumab TTB ratio did not correlate with survival (HR 1.3 (95%CI 0.5-3.3, p=0.60) (Figure 5B). Patients grouped based on the hottest lesion, showed a similar PFS of 5.7 months (SUVpeak ≥6.22) vs. 3.5 months (SUVpeak <6.22) (HR 1.1 (95%CI 0.4-3.0, p= 0.84)).