Radiolabeled immunoglobulin therapy: old barriers and new opportunities

The development of cancer-selective therapies, in particular radiolabeled immunoglobulin therapy (RIT), has stalled. RIT limitations/opportunities are identified in translational research in nude mice, beagles and rhesus monkeys, and in patients with Hodgkin's disease, neurological paraneoplastic syndromes or small vessel vasculitis. Intravenous RIT is most successful in patients with hematological malignancies due to high tumor uptake and long tumor retention of radiolabeled immunoglobulins. Patients with solid tumors are only expected to benefit from RIT by the administration of radiolabeled immunoglobulins directly into the tumor. Tumor-reactive IgG is the best vehicle for i.v. RIT. Tumor-reactive IgM is the best vehicle for intratumoral RIT. The authors do not intend to review the whole clinical RIT experience, but instead analyze the current limitations to success and how they can be circumvented. When the scientific community can reach a consensus on the development and use of these promising and economical radiopharmaceuticals, increasing numbers of patients with recurrent cancer will start to benefit from RIT.