Comparison of Dosimetry Models and Dose Thresholds for Predicting Pathologic Response to Yttrium-90 Radioembolization with Glass Microspheres.

Purpose: This study evaluated pathologic response to ablative transarterial radioembolization (TARE) and compared single-compartment, mean tumor dose, and voxel-based dosimetry thresholds for hepatocellular carcinoma (HCC).

Materials And Methods: This is a retrospective, single-center study which included consecutive patients treated with glass microsphere TARE for a previously untreated HCC followed by liver transplantation between January 2015 - December 2024. A complete response (CR) was assigned if explant pathology showed complete pathologic necrosis (CPN) and if the patient had not undergone further treatments to the tumor. The standard single-compartment, dual-compartment mean tumor, and voxel-based doses were compared for patients with CR and without.

Results: Of the forty-three patients included, 29 had a CR. The only single-compartment dose threshold significantly associated with CR was ≥ 400 Gy, with a positive predictive value (PPV) of 77%. Mean tumor dose thresholds of ≥ 300 and ≥ 400 Gy were associated with CR (PPV 75 and 76%, respectively). The highest PPV for CR observed was for the voxel-based dose threshold of D95 ≥ 500 Gy, at 88%. Single-compartment, dual-compartment mean tumor, and D95 doses were all significantly associated with the likelihood of CR in separate multivariable logistic regression analyses. The incidence of AEs did not vary significantly based on the tested dose thresholds.

Conclusion: Increasing the single- and dual-compartment dose thresholds beyond ≥ 400 Gy did not result in significant associations with CR nor improved PPV. In contrast, D95 ≥ 500 Gy was significantly associated with CR with the highest observed PPV.

Level Of Evidence: Level 3, Local Non-random Sample.