Abstract
1203
Objectives The optimal targeting of radiation and minimizing delivery of activity to normal structures is considered an important goal during intra-arterial brachytherapy. This study was done to compare prescribed Y-90 activity in radioembolization with resin vs glass microspheres.
Methods Patients included in this IRB- approved, retrospective study had liver metastases from colorectal carcinoma and received radioembolization with either glass or resin microspheres. Glass microsphere activity was calculated using manufacturer recommended formula, which uses lobar volumes and considers 120 Gy as the target dose to liver. Resin microsphere activity was calculated using the manufacturer recommended formula based on BSA and tumor volume. Each of these patients were evaluated with CT, PET-CT and/or MRI for contouring and calculation of tumor, lobar and total liver volumes prior to intra-arterial brachytherapy. Group I: 13 patients underwent 22 treatments with resin microspheres, and activity was calculated as if they were to undergo treatment with glass microspheres. Group II: 15 patients underwent 29 treatments with glass microspheres, and activity was calculated as if they were to undergo treatment with resin microspheres. Comparison of actual prescribed and projected activity was done in each group.
Results In group I, if resin microsphere patients were treated with glass microspheres, the average activity prescribed would be higher by 137% (1.05 GBq to 2.48 GBq). In group II, if glass microsphere patients were treated with resin microspheres, the average activity prescribed would be lower by 53% (1.77 GBq to 0.84 GBq).
Conclusions Assuming comparable outcomes in both these groups, prescribed resin microsphere activity is significantly less, on average less than half the prescribed glass microsphere activity. This raises the question whether radiation dosage to normal liver tissue can be minimized using resin microspheres in radioembolization of colorectal liver metastases.
Research Support Sirte