PNNL

Abstract

Patients with relapsed or refractory mantle cell lymphoma (MCL) demonstrate poor survival after standard treatment. Myeloablative radioimmunotherapy (RIT) using 131I tositumomab (anti-CD20) has the ability to deliver specific radiation abosorbed 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 131I tositumomab (mean = 348 MBq), to calculate the required amount of radioactivity for therapy, based on MIRD schema. RESULTS: Mean organ residence times (hr) corrected for 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 NHL. Patients received a mean activity of 21 GBq of 131I (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 131I 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.