OBJECTIVES

To assess the temporal evolution and interobserver agreement of the early categories per the liver imaging reporting and data system (LI-RADS) radiation treatment response assessment (TRA) algorithm in patients receiving selective internal radiation therapy (SIRT) with Yttrium-90 for hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

This single-center retrospective study included consecutive patients with treatment-naïve HCC who underwent serial contrast-enhanced CT/MRI before and after SIRT. Three masked radiologists independently evaluated response at 3-6 months. Another senior radiologist assessed response at 9, 12, 15, 18, 21, 24, and > 24 months after comprehensive review of available clinical-radiological information.

RESULTS

65 patients (mean age, 66.7 ± 11.2 years; 48 men) were included. At 3-6 months after SIRT, 47.7% (31/65) of lesions were assigned to the nonprogressing category, and the remaining 52.3% (34/65) to the nonviable category. Among early nonprogressing lesions, 64.5% (20/31) regressed to the nonviable category, 25.8% (8/31) remained nonprogressing, and 9.7% (3/31) evolved into the viable category at ≥ 12 months. The nonprogressing category decreased in number over time, with 61.3% (19/31) conversion to the nonviable category at 9 months. Among the early nonviable lesions, 91.2% (31/34) remained nonviable at ≥ 12 months, and 8.8% (3/34) evolved into the viable category. Agreement for the 3-6 months LR-TR category assignment was moderate (kappa = 0.46) with CT but almost perfect (kappa = 0.85) with MRI.

CONCLUSIONS

SIRT induced a delayed and sustained response in the majority of HCC patients after ≥ 12 months. MRI demonstrated superior agreement over CT in assessing response at 3-6 months.

KEY POINTS

Question Tumor response to SIRT can change; there is limited evidence on the evolution of the imaging appearance of HCC following SIRT. Findings Sixty-four and five-tenths of early nonprogressing lesions regressed to nonviable, and 91.2% of early nonviable lesions remained free of viability. LR-TR category assignment agreement was moderate with CT but almost perfect with MRI. Clinical relevance SIRT induced a delayed and sustained response in HCC, underscoring the necessity of dynamic evaluation of long-term changes in treated lesions. MRI with subtraction imaging may be preferred over CT for long-term monitoring, which may help prevent premature retreatment decisions.