Role of ⁶⁴CuCl₂ PET/CT in Detecting and Staging Muscle-Invasive Bladder Cancer: Comparison with Contrast-Enhanced CT and ¹⁸F-FDG PET/CT.

Abstract

Molecular imaging of muscle-invasive bladder cancer (MBC) is restricted to its locoregional and distant metastases, since most radiopharmaceuticals have a urinary excretion that limits the visualization of the primary tumor. ⁶⁴CuCl₂ _, a positron-emitting radiotracer with nearly exclusive biliary elimination, could be well suited to exploring urinary tract neoplasms. In this study, we evaluated the feasibility of ⁶⁴CuCl₂-based staging of patients with MBC; furthermore, we compared the diagnostic capability of this method with those of the current gold standards, that is, contrast-enhanced CT (ceCT) and ¹⁸F-FDG PET/CT. <b>Methods:</b> We prospectively enrolled patients referred to our institution for pathology-confirmed MBC staging/restaging between September 2021 and January 2023. All patients underwent ceCT, ¹⁸F-FDG, and ⁶⁴CuCl₂ PET/CT within 2 wk. Patient-based analysis and lesion-based analysis were performed for all of the potentially affected districts (overall, bladder wall, lymph nodes, skeleton, liver, lung, and pelvic soft tissue). <b>Results:</b> Forty-two patients (9 women) were enrolled. Thirty-six (86%) had evidence of disease, with a total of 353 disease sites. On patient-based analysis, ceCT and ⁶⁴CuCl₂ PET/CT showed higher sensitivity than ¹⁸F-FDG PET/CT in detecting the primary tumor (<i>P</i> < 0.001); moreover, ⁶⁴CuCl₂ PET/CT was slightly more sensitive than ¹⁸F-FDG PET/CT in disclosing soft-tissue lesions (<i>P</i> < 0.05). Both PET methods were more specific and accurate than ceCT in classifying nodal lesions (<i>P</i> < 0.05). On lesion-based analysis, ⁶⁴CuCl₂ PET/CT outperformed ¹⁸F-FDG PET/CT and ceCT in detecting disease localizations overall (<i>P</i> < 0.001), in the lymph nodes (<i>P</i> < 0.01), in the skeleton (<i>P</i> < 0.001), and in the soft tissue (<i>P</i> < 0.05). <b>Conclusion:</b> ⁶⁴CuCl₂ PET/CT appears to be a sensitive modality for staging/restaging of MBC and might represent a "one-stop shop" diagnostic method in these scenarios.