Radioimmunotherapy of human colon cancer xenografts by using 131I labeled-CAb1 F(ab')2

Purpose: Therapeutic efficacy, suitable dose, and administration times of 131I-CAb1 F(ab')2, a new monoclonal antibody therapeutics specifically directed against a cell surface-associated glycoprotein of colon cancer, were investigated in this article. Methods and Materials: In human colon cancer xenografts, 131I-CAb1 F(ab')2 at the dose of 125 μCi, 375 μCi, and 1125 μCi were administrated intraperitoneally on Days 6 and 18 after implantation of HR8348 cells with CAb1 high reactivity. Survival time and tumor growth inhibition rate were used to evaluate the efficacy and safety of 131I-CAb1 F(ab')2 in treatment of colon cancer xenografts. Results: Treatment of 125, 375, and 1125 μCi 131I-CAb1 F(ab')2 did not significantly decrease the mean survival time of nude mice when compared with nontreated groups (p = 0.276, 0.865, 0.582, respectively). Moreover, the mean survival times of nude mice receiving 375 μCi and 1125 μCi 131I-CAb1 F(ab')2 were significantly longer than that of 5-FU-treated groups (p 0.018 and 0.042). Tumor growth inhibition rates of the first therapy were 35.67% and 41.37%, with corresponding 131I-labeled antibody dosage of 375 μCi and 1125 μCi. After single attack dosage, second reinforcement therapy may rise efficacy significantly. Tumor growth inhibition rates of 125 μCi, 375 μCi, and 1125 μCi 131I-labeled antibody on Day 20 posttherapy were 42.65%, 56.56%, and 84.41%, respectively. Histopathology examination revealed that tissue necrosis of various degrees was found in 131I-CAb1 F(ab')2-treated groups. Conclusion: 131I-CAb1 F(ab')2 is safe and effective for colon cancer. It may be a novel and potentially adjuvant therapeutics for colon cancer