Optimization of activity and absorbed doses calculation to target/tumor and normal liver volumes in patients submitted to yttrium-90 radioembolization with glass microspheres

Abstract

Introduction The model provided by manufacturers of the Y-90 microspheres does not consider dose restrictions to tumor and to normal liver volumes, but simply calculates activity to be administered based on a prescribed dose of 120 Gy corrected for liver volumes and hepato-pulmonary shunt. It is paramount to analyze data post Y-90 injection, creating dose volume histograms (DVH), to calculate the real absorbed dose distribution in liver segments with and without tumor. Purpose To investigate new algorithms to calculate activities during Y-90 glass microspheres liver radioembolization and optimizing absorbed doses to tumor/target and normal liver volumes. Materials and methods This is a retrospective study of eleven patients with multiple colorectal liver metastases submitted to liver radioembolization with Y-90 glass microspheres (Therasphere TM ). CT and Y-90 PET images were used together with Stratos TM software to obtain values for absorbed doses (based on distribution of Y-90) throughout the entire liver volume. Dose volume histograms (DVH) were created to stratify absorbed dose as percentage of total irradiated volume. Results Our results reveal that only 7% of the liver volume received twice and/or trice the intended prescribed dose of 120 Gy. 25% and 68% of the liver volume received respectively 120 and less than 50 Gy. All patients receiving less than 80 Gy in more than 50% of the liver volume are alive and well. Conclusion Our data suggest a relationship between patient clinical outcome and absorbed doses in liver volumes. Work to optimize administered activities according to tumor/target and normal liver volumes is underway. Disclosure None.