Comparative Physical and Pharmacologic Characteristics of Iodine-131 and Yttrium-90: Implications for Radioimmunotherapy for Patients with Non-Hodgkin's Lymphoma

Abstract

Radioimmunotherapy (RIT) is a promising new treatment option for patients with relapsed/refractory non-Hodgkin's lymphoma. Clinical trials have demonstrated that both iodine-131 (¹³¹I) and yttrium-90 (⁹⁰Y) are suitable radionuclides for RIT. Iodine-131 and ⁹⁰Y differ markedly in their physical properties including half-life, path length, type of energy emissions, intracellular stability, and the organs targeted by the free radionuclide. Both radionuclides can be safely administered in the outpatient setting under current Nuclear Regulatory Commission guidelines. Potential advantages of ¹³¹I for RIT include availability, stable chemistry, longer half-life, and an emission spectrum that allows for dosimetric studies and therapy with the same immunoconjugate. By contrast, ⁹⁰Y has a longer path length and superior intracellular stability compared with ¹³¹I. Yttrium-90 may therefore be preferable to ¹³¹I for patients with bulky disease, poorly vascularized solid tumors, or when targeting internalized antigens. Although ⁹⁰Y emits no gamma photon, dosimetry studies for ⁹⁰Y RIT can be performed using a surrogate radionuclide such as indium-111. Both ¹³¹I- and ⁹⁰Y-labeled anti-CD20 antibodies have demonstrated efficacy in treating relapsed/refractory non-Hodgkin's lymphoma. Further studies are needed, however, to determine if the differences in the pharmacology of ¹³¹I and ⁹⁰Y are clinically relevant.

• Anti-B1
• CD20
• Radioimmunotherapy