Segmental Yttrium-90 Radioembolization with Day-of-Calibration Resin Microspheres: Durable Transarterial Ablation for...

Several recent studies report safety and efficacy of resin yttrium-90 radiation segmentectomy for localized hepatocellular carcinoma. Data informing tumor dose, angiosome dose, and spheres/mL required for ablative-intent resin radioembolization are incomplete. The safety, efficacy, dosimetry, and explant pathology of radiation segmentectomy with day-of calibration (DOC) spheres are reported.

Patients were identified at a tertiary care institution who received radiation segmentectomy with DOC resin during a 10-year period. Post-Y90 dosimetry was performed with Medical Image Merge (MIM) Software. Imaging response, 30-day toxicities, explant pathology, duration of response, and overall survival were analyzed. Associations between dosimetric variables and durable response were tested with receiver operator characteristic, Wilcoxon, and odds ratio analyses.

Twenty tumors in 20 patients were treated, median size 2.6 [range 1.4-6.3] cm. Fifteen patients (75%) were male; median age 68 [range 48-88] years. Seventeen patients (85%) had Child A cirrhosis, 12 from hepatitis C; 15/20 were AlBi grade 2. Sixteen single-vessel and four double-vessel (split dose) treatments reached stasis in 17/24 (71%) infusions. Median tumor and angiosome dose were 263 [range 83-649] and 139 [31-392]. Median lowest dose to any portion of a treated tumor was 147 [29-299] Gy. Median tumor sphere concentration was 79 k [23-206 k] spheres/mL. Local modified REsponse Evaluation Criteria in Solid Tumors (mRECIST) response rates were 18 (90%) complete (16 durable), one partial response, and one stable disease. Two patients experienced adverse events: one at grade 3 and the other at grade 2. Median follow-up was 20 [range 4-126] months. Median duration of response was 47 months. Median overall survival was > / = 94 months both with and without censoring patients at transplant. All six explants demonstrated complete pathologic necrosis. Smaller tumor volume was associated with durable complete response (AUC 0.96), as was infusion to stasis (OR 18 [95% CI 1.19, 271]). Smaller tumor volume and lower angiosome dose were associated with stasis (p = 0.013, 0.035).

Day-of calibration resin segmentectomy treating to stasis is safe and may yield highly durable ablative outcomes for HCC under 3 cm diameter at lower doses than recommended for glass or pre-calibrated resin Y90. Use of more spheres or higher dose targets is likely warranted for larger tumors.