Outpatient radioimmunotherapy with Bexxar. Closed, clean air reservoir minimizes personnel radiation exposure.

Abstract

Radioimmunotherapy (RIT) with Bexxar (tositumomab and iodine-131 tositumomab; Coulter Pharmaceutical, South San Francisco, CA) has been shown to be effective in the treatment of low-grade and transformed low-grade non-Hodgkin lymphoma (NHL). Patient-specific dosimetry with 5 mCi of iodine-131 tositumomab preceded by 450 mg of tositumomab was utilized to calculate the radionuclide dose needed to deliver 75 cGy whole-body radiation (65 cGy for platelet counts of 100,000-149,000/mm(3)). To safely infuse the approximately 95 mCi (range, 52-211mCi) of iodine-131 needed for this treatment, a shielded, closed system was developed to minimize radiation exposure for personnel administering the treatment infusions and to eliminate possible release of aerosolized iodine-131. Twenty-five patients who could be evaluated were infused with a single course of iodine-131 tositumomab therapy and achieved a 76% total response rate at 3 months (32% complete response [CR], 44% partial response [PR]); 59% total response at 6 months (40% CR, 18% PR); and 38% total response at 12 months (31% CR, 6% PR). Administration of RIT using our unique, totally closed system significantly reduced personnel exposure and potential for radioactive spills. The sum of all individuals who administered and monitored the infusions was < 120 mRem whole body exposure over 22 months, well within the ALARA (as low as reasonably achievable) Level I guideline limits. No radioiodide was detectable in the thyroid of any staff member. In NHL patients who had experienced failure with conventional therapy, RIT with iodine-131 tositumomab therapy was safe and effective. Response rates obtained were equivalent to those obtained at the university medical centers where the Phase I-III clinical trials were performed.