Radioimmunodetection of recurrence of colorectal cancer using monoclonal antibody

放射性标记的肿瘤相关抗原单克隆抗体（MAb）显像是一种潜在的特异性定性诊断方法。通过用纯化的CEA免疫产生针对CEA的MAbCEA 102，并用作用于结肠直肠癌成像的放射性示踪剂。为了研究放射性标记的CEA 102的特异性蓄积，使用Fuji计算机X射线摄影（FCR）进行放射自显影研究，并且观察到131-I标记的CEA 102主要定位于原发性肿瘤甚至小的肝转移瘤。然后，我们将131-I标记的CEA 102应用于20例肝转移、局部复发和/或原发性肿瘤。总体灵敏度为71.4%，未观察到假阳性。由于~（131）I具有高能γ射线放射性，且游离~（131）I在膀胱中有较高的蓄积，因此我们尝试使用~（111）In作为放射性示踪剂，其半衰期短，可用于单光子发射CT（SPECT）。我们应用111-In标记的CEA 102对10例患者（原发肿瘤1例，回肠CEA产生肿瘤1例，直肠癌局部复发8例）进行了治疗。总体灵敏度为70%。虽然由于111-In在肝脏中的高蓄积性，该放射性示踪剂不适合于检测肝转移，但它对直肠癌局部复发的诊断有很大的帮助，表明放射性显像在定性诊断方面具有很大的潜力。

Imaging using radiolabeled monoclonal antibody (MAb) to tumor-associated antigen is potentially specific approach to qualitative diagnosis. The MAbCEA102 against CEA was produced by immunization with purified CEA,and used as a radiotracer for the imaging of colorectal cancer. To investgate the specific accumulation of radiolabeled CEA102, autoradiographic study using Fuji Computed Radiography (FCR) was performed, and predominant localizations of 131-I-labeled-CEA102 were observed in primary tumors and even small liver metastases. We then applied 131-I-labeled-CEA102 to 20 cases with liver metastases, local recurrences, and/or primary tumors. Overall sensitivity was 71.4%, and no false positive was observed. Since 131-I has energic gamma-ray emission, and high accumulation of free 131-I in bladder, we attempted using 111-In as a radiotracer which has a short half life and provides to use Single Photon Emission CT (SPECT) . We applied to 10 cases (primary tumor 1, CEA producing tumor of ileum 1, and local recurrence of rectal cancer 8) using 111-In-labeled CEA102. Overall sensitivity was 70%. Although this radiotracer was not suitable to detect liver metastasis due to high accumulation of 111-In in liver, it was especially useful to diagnose local recurrence of rectal cancer using Emission CT.The above results demonstrated that radioimaging has a great potential in qualitative diagnosis.