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

Abstract

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 ((111)In-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 (111)In-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 (18)F-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 < or =2 cm (n=2), with no visualization of most lesions < or = 2 cm (n=9). No (111)In-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 (111)In-hu3S193 antibody targeting to SCLC lesions >2cm, while lesions < or =2 cm reveal a limited targeting.