Variability of response to rituximab on preestablished lymphoma tumors. (A) Bioluminescent imaging pictures: a group of 37 mice was administered 20 mg/kg rituximab on day 13 and 23% of CR, 59% of PR, and 18% of PD were observed. (B) In vivo tumor growth assessed by BLI in mice in PD (▼), PR (■), or CR (●) after infusion of 20 mg/kg rituximab (P < .001). (C) Survival was significantly increased in mice in CR (●) compared with those in PR (■), PD (▼), or control group receiving PBS (△) on D13. *P < .05.