179 - COnsortium on Best Practice for RAdiation Segmentectomy (COBRAS) with Glass Microspheres: A U.S. Multicenter Study Evaluating Predictors of Complete Pathologic Necrosis in Hepatocellular Carcinoma Prior to Liver Transplantation

Monday, April 13, 2026

3:00 PM - 3:09 PM ET

Author/Co-author(s)

ZB

Zachary Berman, MD

Associate Professor of Clinical Radiology
University of California, San Diego, United States

Presenting Author(s)

Cynthia De La Garza Ramos, MD

Interventional Radiology Resident
Department of Radiology, Division of Interventional Radiology, Mayo Clinic, Jacksonville, FL 32224, United States, United States

Author/Co-author(s)

Ali Montazeri, MD, MPH

Radiology Resident
Mayo Clinic Florida, United States
Kurt Pianka, BS (he/him/his)

Medical Student
University of California San Diego, United States
CM

Christopher Malone, MD

Associate Professor
Mallinckrodt Institute of Radiology, Washington University, United States
TS

Tyler Sandow, MD

Interventional Radiologist
Ochsner Health, United States
Juan Gimenez, MD

Interventional Radiologist
Oschner Health, United States
Shamar Young, MD

Professor
University of Arizona, United States
NF

Nicholas Fidelman, MD

Professor
University Of California San Francisco, United States
Edward Kim, MD

Professor of Radiology and Surgery
Mount Sinai Health System, United States
Siddharth Padia, MD

Professor
David Geffen School of Medicine at UCLA, United States
Beau B. Toskich, MD, FSIR

Professor
Mayo Clinic, United States

Purpose: Complete pathologic necrosis (CPN) at liver transplantation (LT) is a positive predictor of freedom from recurrence and overall survival for patients with hepatocellular carcinoma (HCC). Yttrium-90 radiation segmentectomy (RS) CPN rates at explant have been described by small multi-institutional experiences, but consensus for comprehensive authorized user recommendations remain undefined. A national consortium was assembled to establish definitive parameters for RS to optimize CPN.

Materials and Methods: A retrospective, Institutional Review Board approved, multicenter study conducted in seven liver transplant centers across the United States from 2016 to 2024 was performed. All consecutive patients with targeted tumor treatment-naïve HCC who underwent radiation segmentectomy using Y90 glass microspheres (Therasphere™, Boston Scientific, Marlborough, MA) prior to liver transplantation were included. Patients treated with RS, but not subsequently transplanted, were excluded from the analysis. Treatment parameters were compared for patients who achieved CPN vs those without CPN.

Results: A total of 364 treatment-naïve tumors with a median size of 2.4 cm (IQR 2.0-3.1) demonstrated a CPN rate of 68% (n=246). Tumors with CPN had a higher median microsphere activity (1242 vs 1203 Bq; p< 0.001), microspheres per mL (9.0 vs 7.6 x10³/mL; p=0.023), single-compartment dose (544 vs 379 Gy; p< 0.001), and angiosome-to-tumor volume ratio (25.2 vs 15.6; p=0.017). CPN rates at liver transplantation were optimized when a microsphere activity ≥1087 Bq, microsphere per mL ≥8x10³/mL, dose ≥440 Gy, and an angiosome-to-tumor volume ratio (ATR) ≥ 16 were achieved based on a multivariate analysis. There was a direct correlation between the number of optimized parameters and CPN at liver transplantation, with a PPV of 74% with one threshold met and 91% with all thresholds met (p< 0.001). These findings were observed in the overall cohort as well as at each participating center and were reproducible in an internal validation cohort.

Conclusion: Glass microsphere RS achieved high CPN rates, which directly correlated with optimized treatment parameter thresholds. Therapy with microsphere activity ≥1087 Bq (up to 5 days post calibration), with over 8,000 microspheres per mL, a dose above 440 Gy, and an ATR ≥ 16 is recommended as a comprehensive standard for authorized users.