Relationship Between Dose and Local Control in Five-fraction Stereotactic Body Radiotherapy for Hepatocellular Carcinoma

To retrospectively analyze the relationship between local control (LC) and the minimum dose covering 95% of the planning target volume (PTV D95%) in patients with hepatocellular carcinoma (HCC) treated with stereotactic body radiotherapy (SBRT). Between May 2020 and March 2024, 72 HCC tumors in 59 patients were evaluated at Yokohama City University Medical Center. The prescribed dose ranged from 30-50 Gy in five fractions in accordance with the RTOG 1112 trial. However, PTV D95% was used for evaluation because of dose reductions near organs at risk. The median follow-up period was 20 months. During this period, 13 patients died, and nine local recurrences were observed. The median PTV D95% was 38.9 Gy (range=10.6-48.5 Gy). The 1- and 2-year LC rates were 93.7% and 82.3%, respectively. Both univariate and multivariate analyses identified PTV D95% as a significant prognostic factor for LC [univariate: hazard ratio (HR)=0.882, 95% confidence interval (CI)=0.797-0.977, p=0.016; multivariate: HR=0.891, 95%CI=0.891-0.989, p=0.031]. Notably, no local recurrences were observed in patients with PTV D95% ≥40 Gy. Receiver operating characteristic analysis determined that 38 Gy was the optimal PTV D95% cut-off to prevent local recurrence, based on Youden's index. PTV D95% was a significant prognostic factor for LC in patients with HCC treated with five-fraction SBRT. These findings suggest that PTV D95% ≥40 Gy should be considered as a cut-off dose to prevent recurrence.