Integrated treatment using intraperitoneal radioimmunotherapy and positron emission tomography-guided surgery with 64Culabeled cetuximab to treat early- and late-phase peritoneal dissemination in human gastrointestinal cancer xenografts

Abstract

Peritoneal dissemination is a common cause of death from gastrointestinal cancers and is difficult to treat using current therapeutic options, particularly latephase disease. Here, we investigated the feasibility of integrated therapy using 64Cuintraperitoneal radioimmunotherapy (ipRIT), alone or in combination with positron emission tomography (PET)-guided surgery using a theranostic agent (64Cu-labeled anti-epidermal growth factor receptor antibody cetuximab) to treat early- and latephase peritoneal dissemination in mouse models. In this study, we utilized the OpenPET system, which has open space for conducting surgery while monitoring objects at high resolution in real time, as a novel approach to make PET-guided surgery feasible. 64Cu-ipRIT with cetuximab inhibited tumor growth and prolonged survival with little toxicity in mice with early-phase peritoneal dissemination of small lesions. For latephase peritoneal dissemination, a combination of 64Cu-ipRIT for down-staging and subsequent OpenPET-guided surgery for resecting large tumor masses effectively prolonged survival. OpenPET clearly detected tumors (≥3 mm in size) behind other organs in the peritoneal cavity and was useful for confirming the presence or absence of residual tumors during an operation. These findings suggest that integrated 64Cu therapy can serve as a novel treatment strategy for peritoneal dissemination.