BASIC SCIENCE INVESTIGATIONS A Practical Methodology for Patient Release After Tositumomab and 131I-Tositumomab Therapy

A methodology was developed determining patient releasability after radioimmunotherapy with tositumomab and 131I-tositu-momab for the treatment of non-Hodgkin’s lymphoma. Meth-ods: Dosimetry data were obtained and analyzed after 157 administrations of 131I-tositumomab to 139 patients with re-lapsed 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 dosimet-ric 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 thera-peutic infusion. Patient-specific calculations based on the mea-sured total-body residence time and dose rate for 131I-tositu-momab were derived to determine the patient’s maximum releasable dose rate at 1 m, estimated radiation dose to maxi-mally exposed individuals, and the amount of time necessary to avoid close contact with others. Results: The mean adminis-tered 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 wa