Fractionated radioimmunotherapy using low doses of iodine-131 labeled anti-CEA monoclonal antibody after tumor volume reduction

Objective To assess the efficacy of fractionated administration of radiolabeled monoclonal antibody in the treatment of metastases after tumor volume reduction surgery, various experimental therapies were studied comparatively. Methods A total of 200 inbred mice received tumor implantation from a murine adenocarcinoma cell line. The mice were randomly grouped to give saline, Arc-a, I-131-C50 in single or fractionated doses, cold C50, or non-specific I-131-IgG with or without surgical removal of the implanted tumor xenograft. Results In comparison to controls, animals receiving Arc-a and radioactive agents had longer survival, smaller tumor, better clinical condition, and less metastases foci. The best therapeutic response was noted after fractionated doses of I-131-C50, which showed better results in every aspect than those treated with other modalities. The favorable outcome was even more pronounced after tumor volume reduction. Conclusions Fractionated dosing may improve the deposition of radiolabeled monoclonal antibody(McAb) and provide the best therapeutic effect on implanted tumor and metastases. Thus fractionated radioimmunotherapy ( RIT) after tumor volume reduction might be a practical method with promising therapeutic results.