Increased Voxel-Based Y90 Radioembolization Dose to Hepatocellular Carcinoma Improves Imaging Response.

Purpose: To evaluate the relationship between radioembolization tumor dose and imaging response for hepatocellular carcinoma (HCC) treated with radioembolization.

Materials and methods: Retrospective single-institution evaluation of treatment-naïve patients with HCC who underwent TARE between November 2017 and September 2020. Dose-volume histograms (DVHs) were calculated from post 90Y single-photon emission computed tomography. Cross-sectional imaging was obtained at 3 months after radioembolization and evaluated by three blinded abdominal radiologists.

Results: Forty-one patients underwent radioembolization who met the inclusion criteria. Median age was 67 years (range 41-84); 11 were female. At 3 months, 23/41 (56%) had complete response (CR), 9/41 (22%) had partial response (PR), and 8/41 (20%) had stable disease (SD) by mRECIST criteria. DVH analysis demonstrated that increased dose to different tumor volumes was predictive of a complete imaging response at 3 months (p < 0.05 for all). Receiver operating characteristic (ROC) analysis demonstrated a dose threshold of 687 Gy to 95% of the tumor volume resulted in the highest area under curve (AUC) at 0.86 (CI 0.73-0.95) and a positive predictive value (PPV) of 82% to predict complete response by mRECIST criteria.

Conclusion: Voxel-based dosimetry demonstrates that several dose thresholds are predictive of a complete imaging response by mRECIST criteria. A threshold dose of 687 Gy to at least 95% of the tumor volume led to the highest accuracy in predicting complete response by mRECIST criteria.

Level of evidence: Level 3, Cohort Study.