Dynamic Tumor Tracking (DTT) for Hepatocellular Carcinoma Using the Vero4DRT Gimbaled Linac Stereotactic Body...

Background/Objectives: Stereotactic body radiation therapy (SBRT) is a therapeutic option for hepatocellular carcinoma (HCC). This study reviewed outcomes and toxicities of SBRT for HCC using a gimbal-mounted linear accelerator and real-time monitoring system. Methods: A single-institution, retrospective review of SBRT for HCC using DTT between January 2018 and December 2020 was undertaken. Endpoints included local control (LC) and overall survival (OS). Results: A total of 74 patients with 82 tumors treated were identified. Median follow-up was 40.8 months. LC at 1, 3, and 5 years was 89.6%, 71.0%, and 59.9%, respectively. Median time to local failure was not reached. Median OS was 41.3 months (95% CI 30.7-51.8 months). OS at 1, 3, and 5 years was 89.2%, 60.6%, and 33.9%, respectively. On UVA, GTV ≥ 30 cm³ (p = 0.038), and PTV ≥ 150 cm³ (p = 0.010) were associated with an absolute drop in platelet count by ≥50,000/mm³ within six weeks of SBRT, while prior focal liver treatment (p = 0.097) showed a trend toward significance. Underlying viral cirrhosis (p = 0.033), A6 or higher pre-SBRT Child-Pugh score (p = 0.010), and pre-SBRT platelet count <100,000/mm³ (p = 0.017) were significant for a rise in Child-Pugh score of 2 points or more, and the volume of liver-GTV <1000 cm³ (p = 0.093) approached significance. Conclusions: SBRT using DTT is an effective therapeutic option for selected patients with HCC, providing acceptable local control and toxicity.