Intraoperative radioimmunodetection of colo-rectal cancer using monoclonal antibody B72.3 labelled with 125I

RadioImmunoGuided Surgery (RIGS) is a new technique for the intraoperative identification of primary and recurrent colo-rectal cancer, based on IV injection of monoclonal antibody (MAb) B72.3 radiolabelled with 125I. MAb B72.3 selectively binds to the frequently expressed colo-rectal tumour cell antigen TAG72. A hand-held gamma detecting probe is used intraoperatively to localize radiation emitted by the colo-rectal tumour and by its local or distant metastases. Intraoperative findings obtained with RIGS in 20 patients with primary and/or recurrent colo-rectal cancer are reported. The gamma detecting probe localized the tumour deposits in 80% of patients; small tumour deposits not discovered with conventional diagnostic methods were localized by RIGS in 15% of cases. Intraoperative 'in vivo' gamma counts were compared with 'in vitro' gamma well scintillation counts of the resected specimens; a significant correlation between the two different counting methods was found in 95% of cases (p = 0.001).