High-dose [131I]tositumomab (anti-CD20) radioimmunotherapy and autologous hematopoietic stem-cell transplantation for adults ≥60 years old with relapsed or refractory B-cell lymphoma

Purpose The majority of patients with relapsed or refractory B-cell non-Hodgkin's lymphoma (NHL) are older than 60 years, yet they are often denied potentially curative high-dose therapy and autologous stem-cell transplantations (ASCT) because of the risk of excessive treatment-related morbidity and mortality. Myeloablative anti-CD20 radioimmunotherapy (RIT) can deliver curative radiation doses to tumor sites while limiting exposure to normal organs and may be particularly suited for older adults requiring high-dose therapy. Patients and Methods Patients older than 60 years with relapsed B-cell NHL (B-NHL) received infusions of tositumomab anti-CD20 antibody labeled with 185 to 370 Mbq ( 5 to 10 mCi) [I-131]-tracer for dosimetry purposes followed 10 days later by individualized therapeutic infusions of [ 131I] tositumomab ( median, 19.4 Gbq [ 525 mCi]; range, 12.1 to 42.7 Gbq [ 328 to 1,154 mCi]) to deliver 25 to 27 Gy to the critical normal organ receiving the highest radiation dose. ASCT was performed approximately 2 weeks after therapy. Results Twenty-four patients with a median age of 64 years ( range, 60 to 76 years), who had received a median of four prior regimens ( range, two to 14 regimens), were treated. Thirteen patients (54%) had chemotherapy-resistant disease. The estimated 3-year overall and progression-free survival rates were 59% and 51%, respectively, with a median follow-up of 2.9 years ( range, 1 to 6 years). All patients experienced expected myeloablation with engraftment of platelets (>= 20 K/mu L) and neutrophils ( >= 500/mu L), occurring at a median of 9 and 15 days after ASCT, respectively. There were no treatment-related deaths, and only two patients experienced grade 4 nonhematologic toxicity. Conclusion Myeloablative RIT and ASCT is a safe and effective therapeutic option for older adults with relapsed B-NHL.