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

Background/aim: 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).

Patients and methods: 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.

Results: 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.

Conclusion: 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.