Biokinetics and dosimetry of 188Re-anti-CD20 in patients with non-Hodgkin's lymphoma: preliminary experience.

Background: Radioimmunotherapy is a molecular targeting treatment for high-risk leukemia and lymphoma. Rhenium-188-labeled anti-CD66 monoclonal antibody has been used successfully in patients with high-risk acute myeloid leukemia or myelodysplastic syndrome. Our aim was to establish the biokinetics of (188)Re-anti-CD20 in patients and to evaluate its dosimetry as a target-specific radiopharmaceutical for non-Hodgkin's lymphoma (NHL) radioimmunotherapy.

Methods: Whole-body images were acquired at various times after administration of (188)Re-anti-CD20, obtained from instant freeze-dried kit formulations with radiochemical purity >95%. Regions of interest (ROIs) were drawn around source organs in each time frame. The cpm of each ROI was converted to activity using the conjugate view counting method. The image sequence was used to extrapolate time-activity curves in each organ to calculate the total number of disintegrations (N) that occurred in the source regions. N data were the input for the OLINDA/EXM code to calculate internal radiation dose estimates.

Results: Dosimetric studies indicated that after administration of 4.87-8.72 GBq of (188)Re-anti-CD20, the absorbed dose to total body would be 0.75 Gy, which corresponds with the recommended dose for NHL therapies.

Conclusions: The calculated absorbed doses of (188)Re-anti-CD20 indicate that it may be used in radioimmunotherapy. Therefore, these preliminary data justify a full assessment of the safety, toxicity, and efficacy of (188)Re-anti-CD20 in a clinical study.