Outcomes after Stereotactic Body Radiotherapy for Treatment of Hepatocellular Carcinoma

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Stereotactic body radiotherapy (SBRT) is an effective treatment for hepatocellular carcinoma (HCC), especially for those cases whose location, size, or distance from major vessels preclude the use of other local modalities. This study was undertaken to report the outcomes of HCC after SBRT. We reviewed the treatment characteristics and outcomes of all patients with HCC treated with SBRT between December 2005 and December 2015 at our institution. SBRT doses were converted to biologically effective doses by using a standard linear quadratic model with an α/β ratio of 10 (BED10). Disease progression was analyzed by computed tomography (CT), using the modified Response Evaluation Criteria in Solid Tumors version 1.1 and by estimation of the area of viable tumor (contrast-enhanced areas on CT). Hepatobiliary toxicities (HBT) were graded according to the Common Terminology Criteria for Adverse Events v4.0. Time-to-events were calculated from date of SBRT. A total of 42 patients were included in this study. Median age was 65.5 years (range: 48-83). Liver cirrhosis was present in 26 (61.9%) patients, 23 (54.7%) were HCV-positive and 5 (11.9%) HBV-positive. By Child-Pugh (CP) liver function classification, 30 (71.4%) patients were class A and 12 (28.6%) class B. Median tumor size was 5.1 cm (range: 1.9-12). Thirty-eight (90.4%) patients received transarterial chemoembolization prior to SBRT, with a median interval of 76 days (range: 17-2627) prior to SBRT, while 4 (9.5%) received prior radiofrequency ablation. Median SBRT dose was 40 Gy (range: 22-50) delivered with a median of 5 fractions (range: 1-5). Median follow-up was 43 months (range: 5-143). Median overall survival (OS) was 25 months (14-37, 95% I.C.), with an OS of 76% at 1y and 51% at 2y. Accounting for competing risk of death, the cumulative incidence (CI) of local failure (LF) at 1 year was 17% and 21% at 2 years. The CI of failure within the liver outside the treated region was 55% at 1 year and 64% at 2 years, and the CI of distant failure was 25% at 1 and 2 years after SBRT. Patients treated with higher SBRT doses (BED10 ≥78 Gy, n=24) showed better median OS (37 vs. 14 months, P=0.004) compared to patients receiving lower SBRT doses. Tumor size did not correlate with local control or OS rates. The incidence of acute or late G3+ HBT was of 13% for CP A and and 25% for CP B (P=NS). The most common HBT was total bilirubin elevation at serum. Six (14%) patients presented a drop in CP class at 3 months after SBRT. No case of classic radiation induced liver disease was observed. This study confirms the efficacy of SBRT for the treatment of HCC, even for large tumors, and can be safely delivered with low rates of HBT, especially for patients with preserved liver function.