Low Utilization of External Beam Radiation Therapy for Patients With Unresectable Hepatocellular Carcinoma: An Analysis of the United Network for Organ Sharing Database

Purpose: External beam radiation therapy (EBRT) is a safe and emerging bridging liver-directed therapy (LDT) to liver transplant (LT) for patients with hepatocellular carcinoma (HCC). The prevalence and clinical characteristics of patients receiving EBRT as an LDT for LT have not been evaluated. Our aim was to describe the utilization of EBRT in patients with HCC evaluated for LT in the United States.

Methods and materials: We analyzed United Network for Organ Sharing data from October 2013 to June 2020 and identified patients with HCC who applied for model for end-stage liver disease (MELD) exceptions for LT wait list prioritization. The primary outcome was the period prevalence of EBRT. We examined associations between clinical variables and EBRT and fit survival models with EBRT as a time-varying predictor.

Results: We identified 18,543 patients with HCC with MELD exception applications. EBRT was used in 658 patients (3.5%) either alone (1.2%) or combined with other LDT (2.3%). Transarterial chemoembolization was the most used LDT (59.3%), followed by thermal ablation (27.9%) and radioembolization (15.2%). EBRT prevalence rose by an average of 12.2% per year (P = .001). Use of EBRT differed by geographic region, ranging from 2% to 8% (P < .001). EBRT and no EBRT groups had similar initial MELD score, portal vein thrombosis, tumor diameter, number of tumors, bilirubin, and α-fetoprotein (P > .05). Median time-to-transplant from wait list registration for EBRT versus no EBRT groups was 10 months (95% confidence interval, 9.4-10.9) versus 11.9 months (95% confidence interval, 11.7-12.2; P < .001). Evaluated as a time-varying predictor, EBRT increased the risk of LT by 30% (sub-hazard ratio, 1.30; P < .001), while the effect of EBRT on the risk of wait list removal due to clinical deterioration or death (sub-hazard ratio, 1.07; P = .489) was nonsignificant.

Conclusions: In the United States, EBRT is rarely used compared with other LDTs and exhibits geographic variation. Low EBRT utilization highlights a gap in the treatment armamentarium for HCC.