The value of gamma camera and computed tomography data set coregistration to assess Lewis Y antigen targeting in small cell lung cancer by 111Indium-labeled humanized monoclonal antibody 3S193

AimTo 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 materialsTen 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.ResultsA 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.ConclusionCoregistration 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.