Cumulated Activity Comparison of Cu-/Lu-Labeled Anti-Epidermal Growth Factor Receptor Antibody in Esophageal Squamous Cell Carcinoma Model.

This work aimed at estimating the kinetic parameters, and hence cumulated activity (A), of a diagnostic/therapeutic convergence radiopharmaceutical, namely Cu-/Lu-labeled antibody (Cu-/Lu-cetuximab), that acts as anti-epidermal growth factor receptor. In mice bearing esophageal squamous cell carcinoma tumors, to estimate uptake (K), release rate constant (k), and hence A, a kinetic model analysis was applied to recently published biodistribution data of immuno-PET imaging with Cu-cetuximab and of small-animal SPECT/CT imaging with Lu-cetuximab, including blood and TE-8 tumor. K, k, and A were estimated to be 0.0566/0.0593 g⋅h⋅g, 0.0150/0.0030 h, and 2.3 × 10/4.1 × 10 disintegrations (per gram of TE-8 tumor), with an injected activity of 3.70/12.95 MBq, for Cu-/Lu-cetuximab, respectively. A model is available for comparing kinetic parameters and A of the companion diagnostic/therapeutic Cu-/Lu-cetuximab that may be considered as a step for determining whether one can really use the former to predict dosimetry of the latter.