Aim: To assess the value of data set coregistration of gamma camera and computed tomography (CT) in the assessment of targeting of humanized monoclonal antibody 3S193 labeled with indium-111 (111In-hu3S193) to small cell lung cancer (SCLC). Methods and materials: Ten patients (6 male and 4 female; mean age ± S.D., 60 ± 4 years), from an overall population of 20 patients with SCLCs expressing Lewis Y antigen at immunohistochemical analysis, completed a four weekly injections of 111In-hu3S193 and underwent gamma camera imaging. All had had, as part of their baseline evaluation, Fluorine18 fluoro-2-deoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT). Two readers in consensus retrospectively coregistered the gamma camera images with the CT component of the FDG PET/CT by automatic or manual alignment. The resulting image sets were visually examined and SCLC lesions targeting at coregistered gamma camera and CT was correlated side-by-side with the 18F-FDG uptake. Results: A total number of 31 lesions from SCLC with a thoracic (n = 13) or extrathoracic location (n = 18) were all positive on FDG PET/CT. Coregistration of the gamma camera to the CT demonstrated targeting of antibody to all lesions >2 cm (n = 20) and in a few lesions ≤2 cm (n = 2), with no visualization of most lesions ≤2 cm (n = 9). No 111In-hu3S193 uptake in normal tissues was observed. Conclusion: Coregistration of antibody gamma camera imaging to FDG PET/CT is feasible and allows valuable assessment of 111In-hu3S193 antibody targeting to SCLC lesions >2 cm, while lesions ≤2 cm reveal a limited targeting.
- Humanized monoclonal antibody
- Lewis Y antigen
- Molecular imaging