28 Chapter 2 All patients without a previous nephrectomy had an estimated intermediate prognosis. In total 57% of all patients presented with metachronous metastases at a median interval of 0.7 (range 0–15) months between primary diagnosis and first metastasis. One patient presented with only sub-centimeter indeterminate lung lesions; therefore, lesions were not included in the analyses. Five others had a negative [18F]FDG-PET/CT, of whom one plus two other patients had a negative [89Zr]Zr-DFO-girentuximab-PET/CT. In two patients, the [18F]FDG-PET/CT and/or [89Zr]Zr-DFOgirentuximab-PET/CT revealed brain metastases warranting local treatment with stereotactic radiotherapy and temporary treatment with corticosteroids. Patient characteristics are shown in Table 1, imaging examples are shown in Figure 1. Lesion detection rates of CT, [18F]FDG and [89Zr]Zr-DFO-girentuximab-PET/CT A total of 449 lesions were identified by at least one modality (median per patient, 7; ICR 4.25–12.75). Lesions were located in lung (42%), lymph nodes (22%), bone (10%), soft tissue (8%), adrenal gland (6%), kidney (4%), pancreas (4%) or elsewhere (4%). Lesion detection rates differed across modalities: 56% was visualized by CT (95%CI 50–62). [18F]FDG-PET/CT detected 59% (95%CI 53–65; p = 0.37). [89Zr]Zr-DFO-girentuximab-PET/CT visualized 70%(95%CI 64–75), which was more than CT alone (p < 0.001) or [18F]FDG-PET/ CT alone (p < 0.005). Nine of 449 (2%) lesions were outside the field of view of CT (brain n = 2; lymph nodes in the neck n = 4, bone (extremities) n = 3). Agreement in detecting lesions between modalities was poor; kappa’s −0.12 (95%CI−0.25;0.01), −0.00 (95%CI −0.13;0.12), and 0.20 (95%CI−0.02;0.37) for CT and [89Zr]Zr-DFO-girentuximab-PET/CT, CT and [18F]FDG-PET/ CT, and [89Zr]Zr-DFO-girentuximab-PET/CT and [18F]FDG-PET/CT, respectively. Agreement between two radiologists in identifying lesions on CT was moderate (kappa 0.51; 95%CI 0.42– 0.59), and substantial for three nuclear physicians assessing [89Zr]Zr-DFO-girentuximab-PET/CTs (kappa 0.71; 95%CI 0.60–0.82). Table 1. Patient demographics and clinical characteristics. Parameter Patients (n =42) Sex Male 31 (74%) Female 11 (26%) Age (years) Median (range) 66.1 (44-86) Nephrectomy Yes 36 (86%) No 6 (14%) Histology Pure clear cell 32 (76%) Mixed 10 (24%)
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