Kaplan-Meier cumulative survival plots for athymic mice treated with PRIT or conventional RIT following the establishment of palpable Ramos Burkitt lymphoma xenografts. Mice were treated as described in the legend of Figure 1 and analyzed for survival as a function of time. Treatment groups included mice receiving either (A) anti-CD20 1F5, (B) anti–HLA-DR Lym-1, (C) anti-CD22 HD39, (D) control HB8181 Ab conjugates, or (E,F) a combination of all 3 reagents.