Targeted radio-immunotherapy with Bexxar produces durable remissions in patients with late stage low grade non-Hodgkin's lymphomas.

Patients with low grade (LG) non-Hodgkin's lymphomas (NHLs) typically have a median survival of 8-10 years during which they sustain a series of responses and relapses to therapy. More than 95% of B-cell NHLs express the CD20 surface antigen, affording opportunities for CD20-directed therapy of NHL. Since 1990, 5 trials have tested the safety and efficacy of the murine CD20 MAb Tositumomab and Iodine I 131 Tositumomab (Bexxar therapeutic regimen) in 250 patients with relapsed, refractory, or transformed LG NHL. The I-131 irradiates MAb-bound cells and those within the path length of the isotope. Response rates were 56% (overall) and 30% (complete). With a median follow-up of 44.6 months, 30% of the patients achieved a long-term, durable response; median time to progressive disease or death was 5 years. Thus, a single treatment with Bexxar may produce durable responses and partially reverse the natural history of LG NHL.