TUMOR-LOCALIZATION IN PATIENTS BY RADIOLABELED MONOCLONAL-ANTIBODIES AGAINST COLON-CARCINOMA

Abstract

A radiolabeled monoclonal antibody (MAb) which reacts specifically in vitro and ex vivo to human colorectal carcinoma was administered to 52 colorectal carcinoma patients and 15 patients with other types of cancer. Of 63 colorectal carcinoma tumor sites studied, 34 showed significant accumulation of antibody by external photoscanning and tomoscintigraphy; none of the 20 sites of other cancer types gave positive results. Of the patients, 1/3 received F(ab'')2 fragments of the MAb, which gave a slightly higher percentage (61%) of positive results than did intact MAb (51%). A few patients scheduled for tumor resection were given injections simultaneously of 131I-labeled MAb and 125I-labeled normal IgG. Antibody concentration in resected tumors was 3.6-6.3 times higher than the average antibody concentration in adjacent normal tissues (1.5, 3.4 and 9.4 as compared with normal mucosa, serosa and fat, respectively), and the specificity indices, calculated by differential radioactivity analysis, ranged from 2.1-5.1. The results show the potential value and limitations of this particular MAb for tumor detection by immunoscintigraphy.