Voxel-based Dosimetry Predicting Treatment Response and Related Toxicity in HCC Patients Treated with Resin-based Y90 Radioembolization: A prospective, single-arm study

Abstract Background: There is an increasing body of evidence indicating Y90 dose thresholds for tumor response and treatment related toxicity. These thresholds are poorly studied in resin Y90 particularly in hepatocellular carcinoma (HCC). Purpose: To evaluate the efficacy of prospective voxel-based dosimetry for predicting treatment response and adverse events (AE’s) in patients with HCC undergoing resin-based Y90 radioembolization. Materials and Methods: This correlative study was based on a prospective single-arm clinical trial (NCT04172714) which evaluated the efficacy of low/scout (15 mCi) activity of resin-based Y90 for treatment planning. Partition model was used with the goal of tumor dose (TD) > 200 Gy and non-tumoral liver dose (NTLD) < 70 Gy for non-segmental therapies. Single compartment dose of 200 Gy was used for segmentectomies. Prescribed Y90 activity minus scout activity was administered for therapeutic Y90 followed by Y90-PET/CT. Sureplan® (MIM Software, Cleveland, OH) was used for dosimetry analysis. Treatment response was evaluated at 3 and 6 months. Receiver operating characteristic curve determined TD response threshold for objective (OR) and complete response (CR) as well as non-tumor liver dose (NTLD) threshold that predicted AE’s. Results: N = 30 patients were treated with 33 tumors (19 segmental and 14 non-segmental). One patient died before the first imaging and clinical follow-up was excluded from this analysis. Overall, 26(81%) of tumors had OR and 23(72%) had CR. Mean TD of 253 Gy predicted OR with 92% sensitivity and 83% specificity (area under the curve (AUC = 0.929, p < 0.001). Mean TD of 337 Gy predicted CR with 83% sensitivity and 89% specificity (AUC = 0.845, p < 0.001). Mean NTLD of 81Gy and 87 Gy predicted grade 3 AE’s with 100% sensitivity and 100% specificity in the non-segmental cohort at 3- and 6-month post Y90, respectively. Conclusion: In patients with HCC undergoing resin-based Y90, there are dose response and dose toxicity thresholds directly affecting outcomes.