A few clinical phase I or II trials suggest a certain degree of efficiency of humanized or chimeric anti-CEA mAbs, radiolabeled with either 131Iodine or 90Ytrium, in heavily pre-treated patients with metastatic colorectal cancer (MCRC) CT84.66 [8,14,15]. The gene discussed is CEACAM5; the disease is metastatic colorectal cancer.