Clinical platforms in NET patients treated with radioligand therapy: a dosimetric comparison

Background: this work aims to compare absorbed doses between different platforms developed for Radioligand Therapy (RLT). Data analysis concerned dosimetric monitoring of kidneys and significant lesions (ROIs) in NET patients treated with Lu-177-DOTATOC. We compared absorbed doses between a pure voxel dosimetry approach [1], HMS® OLINDA/EXM 2.0, PLANET® Onco Dose and MIM® MRT [2]. Materials and method: we analyzed data of 10 patients performing sequential SPECT-CT dosimetry at 3 time points. To obtain dose rates with our voxel dosimetry approach, the convolution [1] between the Dose Voxel Kernel (DVK) and patient SPECT data was performed for each time point. Then, the dose-rate curves have been fitted with a bi-exponential function and by integrating this function, the absorbed doses were derived. Finally, we compared these results with those returned by the clinical platforms, processing the same ROIs for each patient. Results: the comparison highlights a discrepancy between the voxel dosimetry approach and PLANET® Onco Dose and MIM® MRT, when the phantom-based voxel dosimetry approach is used. Moreover if MIM® MRT employs the patient-specific voxel dosimetry approach, results agree with the other two procedures. Conclusion: a discrepancy in dosimetry results appears when different workflows are used. An overestimation of absorbed doses within kidneys seems to appear when a phantom-based voxel dosimetry approach is used. For significant lesions, however, it seems not to be a systematic trend. Results need to be validated by increasing the patient cohort dimension.