Monte Carlo single-cell dosimetry of I-131, I-125 and I-123 for targeted radioimmunotherapy of B-cell lymphoma

摘要

Purpose: To study the dosimetric characteristics of a non-internalizing and an internalizing monoclonal antibody (MAb) labeled with 131I, 125I or 123I, which targets a typical lymphoma B-cell. Materials and methods: Using our hybrid Monte Carlo (MC) code which combines detailed- and condensed-history electron track simulation we carry out transport calculations of Auger and beta electrons for different intracellular distributions of radioactivity. Results: Assuming permanent retention of the MAb in cells, 125I gave the highest absorbed dose and 123I the highest absorbed dose rate. Under the more realistic scenario of biologic excretion from the cells, 123I resulted in the highest absorbed dose and absorbed dose rate. Conclusion: The present dosimetric analysis shows that biological half-life, subcellular localization, and the proper account of low-energy electrons is critical in assessing the energy deposition inside the targeted cells from the three iodide radioisotopes examined. From a dosimetric point of view and under the present approximations 123I might be superior to the other two radioiodides in the treatment of microscopic disease in B-cell lymphoma patients.