Abstract
177Lu-lilotomab satetraxetan is a novel antibody radionuclide conjugate (ARC) currently tested in a phase 1/2a first-in-human dosage escalation trial for patients with relapsed CD37+ indolent non-Hodgkin’s lymphoma. The aim of this work was to develop dosimetric methods and calculate tumor absorbed radiation doses for patients treated with 177Lu-lilotomab satetraxetan. Methods: Patients were treated at escalating injected activities (10, 15 and 20 MBq/kg) of 177Lu-lilotomab satetraxetan and with different pre-dosing; with or without 40 mg unlabeled lilotomab. Eight patients were included for the tumor dosimetry study. Tumor radioactivity concentrations were calculated from Single Photon Emission Computer Tomography (SPECT) acquisitions at multiple time points, and tumor masses were delineated from corresponding Computer Tomography (CT) scans. Tumor absorbed doses were then calculated using the OLINDA sphere model. To perform voxel dosimetry, the SPECT/CT data and an in-house developed MATLAB program were combined to investigate the dose rate homogeneity. Results: Twenty-six tumors in 8 patients were ascribed a mean tumor absorbed dose. Absorbed doses ranged from 75 cGy to 794 cGy with a median of 268 cGy across different dosage levels and different pre-dosing. A significant correlation between the dosage level and tumor absorbed dose was found. Twenty-one tumors were included for voxel dosimetry, and parameters describing dose-volume coverage calculated. The investigation of intra-tumor voxel doses indicates that mean tumor dose is correlated to these parameters. Conclusion: Tumor absorbed doses for patients treated with 177Lu-lilotomab satetraxetan are comparable to doses reported for other radioimmunotherapy compounds. Although the inter-tumor variability was considerable, a correlation between tumor dose and patient dosage level was found. Our results indicate that mean dose may be used as the sole dosimetric parameter on the lesion level.
- Oncology: Lymphoma
- Radiobiology/Dosimetry
- Radionuclide Therapy
- Tumor absorbed dose
- antibody radionuclide conjugate
- dose-volume-histogram
- non-Hodgkins lymphoma
- Copyright © 2016 by the Society of Nuclear Medicine and Molecular Imaging, Inc.