30 Chapter 2 Combination of modalities for lesion detection With the addition of [89Zr]Zr-DFO-girentuximab-PET/CT and [18F]FDG-PET/CT, lesion detection by CT alone increased from 56% to 91% (95%CI 87–94) and 84% (95%CI 79–88),respectively. Improved lesion detection rate was apparent for all organ sites (Figure 2). The lesion detection of CT-[89Zr]Zr-DFO-girentuximab-PET/CT was better than CT-[18F]FDG-PET/CT (p < 0.005). Largest improvement was seen in the number of bone lesions, with 81% of all bone lesions detected by both [89Zr]Zr-DFO-girentuximab-PET/CT and CT as well as [18F]FDG-PET/CT with CT, compared to 16% by CT alone (p < 0.001). More lung lesions were detected by CT-[89Zr] Zr-DFO-girentuximab-PET/CT compared to CT-[18F]FDG-PET/CT [95% (95%CI 91–98)] versus 84% (95%CI 76–89; p <0.001). Lesion detection approached 100% in pancreas and kidney with combined CT and [89Zr]Zr-DFO-girentuximab-PET/CT. Conversely, detecting enlarged lymph nodes was better with combined [18F]FDG-PET/CT and CT [94% (95%CI 88–97)], compared to [89Zr]Zr-DFO-girentuximab-PET/CT and CT [83% (95%CI 73–89, p <0.05)]. Assessment of affected organ sites The median number of affected organ sites increased with the addition of [89Zr]Zr-DFOgirentuximab-PET/CT or [18F]FDG-PET/CT compared to CT alone in 27 patients (median increased from 2 to 3, range 1–7 (p < 0.005). [89Zr]Zr-DFO-girentuximab-PET/CT and [18F] FDG-PET/CT performed similarly (Table 2). Patients were categorized according to the location of their lesions (e.g., lung only; other organ(s) only and both lung and other organs). With the addition of both PET/CTs, two patients were re-categorized from lung only into ‘both lung and other organs’ based on the additional detected lymph node and bone lesions (Table 1). Figure 2. Lesion detection per imaging modality and per organ. Concordant pairs were lesions that were visualized on all 3 modalities. 9 PET detected lesions were outside the field of view of CT. *p <0∙001 compared to CT only.