A practical methodology for patient release after tositumomab and 131I-tositumomab therapy

Jeffry A. Siegel, Stewart Kroll, Denise Regan, Mark S. Kaminski, Richard L. Wahl

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


A methodology was developed determining patient releasability after radioimmunotherapy with tositumomab and 131I-tositumomab for the treatment of non-Hodgkin's lymphoma. Methods: Dosimetry data were obtained and analyzed after 157 administrations of 131I-tositumomab to 139 patients with relapsed or refractory non-Hodgkin's lymphoma. Tositumomab and 131I-tositumomab therapy included dosimetric (low activity) and therapeutic (high activity) administrations. For each patient, the total-body residence time was calculated after the dosimetric administration from total-body counts obtained over 6 or 7 d and was then used to determine the appropriate therapeutic activity to deliver a specific total-body radiation dose. Patient dose rates at 1 m were measured immediately after the therapeutic infusion. Patient-specific calculations based on the measured total-body residence time and dose rate for 131I-tositumomab were derived to determine the patient's maximum releasable dose rate at 1 m, estimated radiation dose to maximally exposed individuals, and the amount of time necessary to avoid close contact with others. Results: The mean administered activity (±SD), determined by dosimetry studies for each patient before therapy, was 3,108 ± 1,073 MBq (84 ± 29 mCi) (range, 1,221 ± 5,957 MBq [33-161 mCi]). Immediately after treatment, the mean measured dose rate (±SD) at 1 m was 0.109 ± 0.032 mSv/h (10.9 ± 3.2 mrem/h; range, 0.04-0.24 mSv/h [4-24 mrem/h]). The measured dose rates were 60% (range, 37%-90%; P < 0.0001) of the theoretic dose rates from a point source in air predicted using the dose equivalent rate per unit activity of 131I(5.95 x 10-5 mSv/MBq h [0.22 mrem/mCi h] at 1 m). The mean estimated radiation dose to the maximally exposed individual was 3.06 mSv (306 mrem) (range, 1.95-4.96 mSv [195-496 mrem]). On the basis of current regulatory patient-release criteria, all 131I-tositumomab-treated patients were determined to be releasable by comparing the dose rate at 1 m with a predetermined maximum releasable dose rate. Detailed instructions were provided to limit family members' exposure. Conclusion: A methodology has been developed for the release of patients administered radioactive materials based on the new Nuclear Regulatory Commission regulations. This approach uses a patient-specific dose calculation based on the measured total-body residence time and dose rate. This analysis shows the feasibility of outpatient radioimmunotherapy with tositumomab and 131I-tositumomab.

Original languageEnglish
Pages (from-to)354-363
Number of pages10
JournalJournal of Nuclear Medicine
Issue number3
StatePublished - Mar 20 2002


  • Dosimetry
  • Non-Hodgkin's lymphoma
  • Patient release
  • Radioimmunotherapy


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