Radioimmunotherapy dose estimation in patients with B-cell lymphoma

Trials of radiolabeled antibody therapy in patients with B-cell lymphoma have been the most promising of any in radioimmunotherapy. Response rates of greater than 90% with many complete remissions have been reported by several groups using either low (185-370 MBq) or high (8.6-22.5 GBq) doses of I-131-labeled antibodies against B-cell antigens. Estimated doses delivered to normal organs have ranged from 0.2 to 2.2 mGy/MBq and have shown similar interpatient variation in all series, despite differences in antibody specificity and dosimetric techniques. Tumor doses have ranged from 0.5 to 5.4 mGy/MBq. There has been little correlation of tumor response with estimated tumor dose. Toxicity has been limited to bone marrow suppression which has been greater with the higher amounts of I-131. An advantage for a particular antibody specificity or for high dose compared to multiple low doses has yet to be demonstrated.