Efficacy of 4HPR and rituximab in preventing tumor progression using a minimal disease lymphoma xenograft model. Athymic mice (8 mice per group) were inoculated subcutaneously with 7 × 10⁶ Ramos (Burkitt lymphoma) cells. Seventy-two hours after inoculation, mice were randomly assigned to treatment with 4HPR (250 μg/d, 5 days per week), rituximab (200 μg/wk), 4HPR + rituximab (at the same doses), or solvent only for 4 weeks. Tumor volume in mm³ (y-axis) was measured over time (x-axis). Curves were truncated at the indicated time points when mice in a group required humane killing because of tumor progression. Error bars indicate standard deviation.