PET/CT with 18F-PSMA-1007 in Diagnostics of Metastatic Lesions of Clear-Cell Renal Cell Carcinoma in Comparison with 18F-FDG: Prospective Study

Purpose: To demonstrate the capabilities of PET/CT with 18 F-PSMA-1007 in comparison with 18 F-FDG in the diagnostics of metastatic ccRCC. Material and methods: Ninety-seven patients with metastatic ccRCC were included in the study. Biopsy results of the primary tumor were available in all patients. Metastatic foci were confirmed by biopsy, follow-up and other diagnostic methods. All patients under went PET/CT with 18 F-PSMA-1007 and 18 F FDG. Results: A total of 1247 metastases were identified in 97 patients: 1002 — PSMA-positive, 245 — PSMA-negative, 694 — FDG-positive, and 553 — FDG-negative. The largest number of foci was found in the lungs (601 in 43 patients), bones (220 in 46 patients), and lymph nodes (166 in 34 patients). Sixty-two patients had more PSMA-positive foci compared with 18 FDG, 32 had an equal number of foci, and 3 had more foci according to PET/CT with 18 FDG. The sensitivity and specificity of 18 F-PSMA-1007 in the diagnostics of ccRCC metastases were 80 % and 72 %, positive and negative predictive value were 87 % and 61 %, respectively. The sensitivity and specificity of 18 F-FDG in the diagnostics of ccRCC metastases were 55 % and 54 %, positive and negative predictive value were 69 % and 41 %, respectively. The mean SUV max difference between 18 F-PSMA-1007 and 18 FDG was 5.32, and the mean TBR difference was 5.66. Lung foci demonstrated significantly lower SUV max and TBR for both RPs compared to other metastases. Discussion and conclusions. Data analysis demonstrates higher efficiency of 18 F-PSMA-1007 compared to 18 F-FDG in the diagnostics of ccRCC metastases. PET/CT with 18 F-PSMA-1007 revealed a higher number of metastases, SUV max and TBR in studies with 18 F-PSMA-1007 are on average significantly higher than those with 18 F FDG. PET/CT with 18 F-PSMA-1007 demonstrates the lowest efficiency in the diagnosis of foci in the lungs up to 1 cm. It is feasible to analyze pulmonary foci and other metastases separately to exclude the influence of a large number of low-active and false-negative foci on statistical parameters. PET/CT with 18 F-PSMA-1007 can be recommended for use in patients with suspected metastatic ccRCC as an alternative to routine diagnostic methods and PET/CT with 18 F-FDG. The potential of 18 F-PSMA-1007 in assessing the efficacy of systemic therapy requires further investigation.