Tumor burden influence on response and survival. (A) Response to 20 mg/kg rituximab administered on day 13 was significantly different according to tumor burden (P < .05; n = 37). ○ represents individual values of tumor burden; and ● represents respective means ( ± SD). (B) Three groups of animals with low (< 0.15 × 10⁶ AU, n = 7) ( □ ), intermediate (0.15 × 10⁶ to 3 × 10⁶ AU, n = 24) (△), and high (> 3 × 10⁶ AU, n = 8) (●) tumor burden. Survival was significantly higher for mice with low tumor burden compared with mice with intermediate and high tumor burden; P < .05.