Comparison of radiation dose estimation for myeloablative radioimmunotherapy for relapsed or recurrent mantle cell lymphoma using (131)I tositumomab to that of other types of non-Hodgkin's lymphoma.

UNLABELLED: Patients with relapsed or refractory mantle cell lymphoma (MCL) demonstrate poor survival after standard treatment. Myeloablative radioimmunotherapy (RIT) using (131)I tositumomab (anti-CD20) has the ability to deliver specific radiation-absorbed dose to antigen-bearing tumor. We reviewed normal organ radiation- absorbed doses in MCL patients.

METHODS: Records of patients with MCL (n =25), who received myeloablative RIT between January 1996 and December 2003 were reviewed. Individual patient radiation dosimetry was performed on all patients after a trace-labeled infusion of (131)I tositumomab (mean = 348 MBq), to calculate the required amount of radioactivity for therapy, based on medical internal radiation dose (MIRD) schema.

RESULTS: Mean organ residence times (hour) corrected for computed tomography (CT) derived organ volumes for MCL, were as follows: Lungs: 9.0; Liver: 12.4; Kidneys: 1.7; Spleen: 2.17; Whole Body: 62.4 and mean radiation absorbed doses mGy/Mbq were: Lungs: 1.2; Liver: 1.1; Kidneys: 0.85; Spleen: 1.7; Whole Body: 0.21. This is similar to patients with other non-Hodgkin's lymphoma (NHL). Patients received a mean activity of 21 GBq of (131)I (range, 11.5-41.4) for therapy estimated to deliver 25 Gy to the normal organ receiving the highest radiation-absorbed dose.

CONCLUSION: Myeloablative RIT using (131)I tositumomab results in normal organ radiation-absorbed doses similar to those in patients with other non-Hodgkin's lymphoma, and is suitable for treating patients with relapsed or refractory MCL.