American Society of Hematology

Figure 1

$Figure 1. 131I-rituximab administration. (A) Schematic outline of treatment schedule for rituximab followed by 131I-rituximab. A total of 375 mg/m2 of unlabeled rituximab was administered weekly for 4 weeks, shown as weeks 0, 1, 2, and 3. The dosimetric tracers of 185 MBq of 131I-rituximab were delivered on weeks 7 and 15. The therapeutic fractions of 131I-rituximab were each administered 2 weeks after dosimetry, at weeks 9 and 17. Both the dosimetric tracers and the therapeutic fractions of 131I-rituximab were delivered immediately after an infusion of 100 mg/m2. The dosimetry of 5 patients was assessed with a 185-MBq dosimetric tracer dose of 131I-rituximab before receiving any rituximab. (B) The clearance of 131I-rituximab in patients before rituximab and after the first and second 131I-rituximab tracer dose. The pharmacokinetics of 131I rituximab were calculated using whole-body anterior and posterior gamma camera images obtained within 1 hour after completion of the tracer infusion dose and on days 4 and 6 after 131I-rituximab administration. For the prerituximab group, no rituximab had been administered before the dosimetric studies. For groups marked “dose 1” and “dose 2,” 4 weekly infusions of 375 mg/m2 were given according to the schedule in panel A. For the predose, a further 100 mg/m2 of unlabeled rituximab was administered as an intravenous infusion, followed 2 to 3 hours later by an infusion of 185 MBq 131I-rituximab. (C) 131I-rituximab administered without prior rituximab treatment is mostly sequestered to the spleen. Whole-body gamma camera scanning was performed after administration of 185 MBq 131I-rituximab without any prior rituximab. The radiolabeled rituximab and gamma activity is visualized within the spleen. (D) Biodistribution of 131I rituximab after 4 loading doses of rituximab. After induction therapy with 4 weekly infusions of rituximab (375 mg/m2), the 131I-rituximab no longer localizes to the spleen, and there is a more widespread biodistribution throughout the body. Tumor targeting within known pelvic lymph nodes is observed.$

¹³¹I-rituximab administration. (A) Schematic outline of treatment schedule for rituximab followed by ¹³¹I-rituximab. A total of 375 mg/m² of unlabeled rituximab was administered weekly for 4 weeks, shown as weeks 0, 1, 2, and 3. The dosimetric tracers of 185 MBq of ¹³¹I-rituximab were delivered on weeks 7 and 15. The therapeutic fractions of ¹³¹I-rituximab were each administered 2 weeks after dosimetry, at weeks 9 and 17. Both the dosimetric tracers and the therapeutic fractions of ¹³¹I-rituximab were delivered immediately after an infusion of 100 mg/m². The dosimetry of 5 patients was assessed with a 185-MBq dosimetric tracer dose of ¹³¹I-rituximab before receiving any rituximab. (B) The clearance of ¹³¹I-rituximab in patients before rituximab and after the first and second ¹³¹I-rituximab tracer dose. The pharmacokinetics of ¹³¹I rituximab were calculated using whole-body anterior and posterior gamma camera images obtained within 1 hour after completion of the tracer infusion dose and on days 4 and 6 after ¹³¹I-rituximab administration. For the prerituximab group, no rituximab had been administered before the dosimetric studies. For groups marked “dose 1” and “dose 2,” 4 weekly infusions of 375 mg/m² were given according to the schedule in panel A. For the predose, a further 100 mg/m² of unlabeled rituximab was administered as an intravenous infusion, followed 2 to 3 hours later by an infusion of 185 MBq ¹³¹I-rituximab. (C) ¹³¹I-rituximab administered without prior rituximab treatment is mostly sequestered to the spleen. Whole-body gamma camera scanning was performed after administration of 185 MBq ¹³¹I-rituximab without any prior rituximab. The radiolabeled rituximab and gamma activity is visualized within the spleen. (D) Biodistribution of ¹³¹I rituximab after 4 loading doses of rituximab. After induction therapy with 4 weekly infusions of rituximab (375 mg/m²), the ¹³¹I-rituximab no longer localizes to the spleen, and there is a more widespread biodistribution throughout the body. Tumor targeting within known pelvic lymph nodes is observed.

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