Objective: Carbonic anhydrase 9 recognized by chimeric monoclonal antibody cG250 is overexpressed on biliary cancers. The aim of this study was to determine the targeting of radiolabeled cG250 in patients with biliary cancer to explore a potential role of radioimmunotherapy.
Methods: Three (3) patients received a diagnostic dose 111In-cG250, and images were acquired 2 hours and 5 days after injection. Immediately after the last imaging session, 131I-cG250 was administered and images were acquired after 2 hours and 5 days. Visual and quantitative analyses was performed and tumor- to-background, tumor-to-normal liver-uptake ratios, and tumor uptake were calculated.
Results: Administration of 111In-cG250 in patients with biliary cancer did not reveal enhanced uptake in the cancer lesions on whole-body scans. The scans obtained after the 131I-cG250 administration showed slightly enhanced tumor uptake in 1 patient with cholangiocarcinoma stage II. In 2 patients with gallbladder carcinoma stage IV, neither 111In-cG250 nor 131I-cG250 showed targeting of known tumor lesions. Immunohistochemical analysis demonstrated CAIX expression in all 3 cases. There were no adverse events related to radiolabeled cG250 administration.
Conclusions: 111In- or 131I-labeled cG250 is not suitable for biliary cancer targeting. Therefore, there is no basis to develop radioimmunotherapy based on radiolabeled cG250 in biliary cancer.