Treatment outcomes of helical tomotherapy for hepatocellular carcinoma in terms of intermediate-dose spillage

BACKGROUND: Although helical tomotherapy (HT) tends to increase intermediate-dose spillage by increasing of low-dose region, this has not been fully determined in the clinical setting. Therefore, we investigated treatment outcomes of HT for hepatocellular carcinoma (HCC) with respect to intermediate-dose spillage. METHODS: We retrospectively reviewed 20 HCC patients, who received high-dose radiotherapy (RT) using HT with radical intent between April 2014 and September 2017. In accordance with the Barcelona Clinic Liver Cancer (BCLC) classification, stage was 0 in 7 patients, A in 3 patients, B in 5 patients, and C in 5 patients. Baseline Child-Pugh class was A in 18 patients and B in 2 patients. The median tumor size was 2.5 cm (range, 1–11 cm). Helical intensity-modulated radiotherapy (IMRT) technique was applied in all patients: among these, 13 patients were treated with stereotactic body radiotherapy (SBRT). The median fraction size was 12 Gy (range, 2–15 Gy), and the median total dose was 50 Gy (range, 44–60 Gy). Intermediate-dose spillage was assessed by the Radiation Therapy Oncology Group recommendation from 22 HT planning data, as follows: R50% means the ratio of the 50% prescription isodose volume to the planning target volume (PTV). RESULTS: The median follow-up period after HT was 22 months. The local progression-free survival (LPFS) and progression-free survival (PFS) rates were 89% and 59% at 1 year, and 82% and 30% at 2 years, respectively. The overall survival rate was 100% at 1 year and 85% at 2 years, respectively. In terms of intermediate-dose spillage, minor or major deviations were noted in the R50% of 20 HT plans (91%). However, 1 patient (5%) experienced classic radiation-induced liver disease, and severe toxicity ≥ grade 3 was not reported. CONCLUSIONS: Although HT for HCC tends to increase intermediate-dose spillage, the treatment results were favorable with that reported in other published studies.