OtherCONTINUING EDUCATION

Techniques for Using Bexxar for the Treatment of Non-Hodgkin’s Lymphoma*

David W. Seldin
Journal of Nuclear Medicine Technology September 2002, 30 (3) 109-114;

Article Figures & Data

Figures

  • FIGURE 1.
    FIGURE 1.

    Graphic representation of developmental stages of B-lymphocytes from undifferentiated stem cells to plasma cells. Predominant location of these cell types, degree of expression of CD20 antigen, and associated malignant transformations are shown. CML = chronic myelogenous leukemia; CLL = chronic lymphocytic leukemia.

  • FIGURE 2.
    FIGURE 2.

    Anterior whole-body images from same patient taken 1 h after injection of 131I-tositumomab. (Left) Image shows biodistribution without predose of unlabeled tositumomab, with most activity in spleen. (Right) Image, for which patient had received unlabeled predose, shows markedly less splenic uptake and better visualization of rest of body.

  • FIGURE 3.
    FIGURE 3.

    Total radiation dose from 131I-tositumomab is dependent on rate of biologic clearance of radiopharmaceutical. Patients with rapid clearance require higher treatment dose than those with slow clearance to deliver same absorbed dose. Total administered dose is proportional to area under curve.

  • FIGURE 4.
    FIGURE 4.

    Distribution of administered doses of 131I-tositumomab required to deliver total administered dose of 75 cGy in group of 201 patients enrolled in clinical trials.

  • FIGURE 5.
    FIGURE 5.

    Images (scan speed, 100 cm/min) obtained as part of dosimetric study of patient enrolled in clinical trial. Background and standard images are similar at all time points; changes in distribution and clearance of activity are seen on patient images taken at 3 time points.

Tables

  • TABLE 1

    Sample Data and Calculations from Patient Dosimetric Study

    ParameterDay 0Day 4Day 6
    Dose calibrator measurements
     Time of measurement13:2012:5111:30
     131I standard activity (kBq [μCi])9,694 (262)6,993 (189)5,846 (158)
    Gamma-camera counts (whole-body mode)
     131I source
      Time started13:1112:5211:19
      Anterior counts35,92524,30920,411
     Background
      Time started13:0512:4211:14
      Anterior counts2,5442,5102,345
     Patient
      Time started14:1313:0111:27
      Anterior counts327,581125,24874,381
    Quality control calculation
     Time from initial count (h)095.7142.1
     Background-corrected source counts33,38121,79918,066
     % initial count1006554
     Counts per 37 kBq (μCi) in standard127.4115.3114.3
    Residence time calculation
     Background-corrected patient counts325,037122,73872,036
     % initial count1003822
     Residence time (h) from graph9896
    Therapy dose calculation
     Administered 131I dose
      Embedded Image75.476.9

    • Whole-body scan speed, 100 cm/min; collimator, medium energy; patient platelet count, 133,000; patient height, 165 cm; maximum effective mass (from table), 78.7 kg; camera height above table, 36 cm; whole-body scan field of view, 179 cm; desired total-body dose, 65 cGy; patient weight, 82.5 kg; activity hours (from table), 8,523.

  • TABLE 2

    Calculations for Determining Release Criteria and Length of Time for Observing Precautions After Therapy Dose Administration

    Measured residence time96 h
    Measured dose rate at 1 m after therapy0.1 mSv/h (10 mrem/h)
    Releasable dose rate (from table)0.2 mSv/h (20 mrem/h)
    Calculated exposure to others (0.25 × 0.1 × [7.15 + 0.99 × 96])2.56 mSv (255.5 mrem)
    Duration of precautions from table provided by manufacturer
     Sleep at least 1.83 m from others (0.098 × 96)9.4 d
     Do not take long trip (>4 h) near others (0.019 × 96)1.8 d
     Stay at least 1.83 m from pregnant women and children (<1 mSv [<100 mrem] exposure) (0.135 × 96)13 d
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