Feasibility of stereotactic body radiation therapy with volumetric modulated arc therapy and high intensity photon beams for hepatocellular carcinoma patients

Background: To report technical features, early outcome and toxicity of stereotactic body radiation therapy (SBRT) treatments with volumetric modulated arc therapy (RapidArc) for patients with hepatocellular carcinoma (HCC). Methods: Twenty patients (22 lesions) were prospectively enrolled in a feasibility study. Dose prescription was 50Gy in 10 fractions. Seven patients (35%) were classified as AJCC stage I-II while 13 (65%) were stages III-IV. Eighteen patients (90%) were Child-Pugh stage A, the remaining were stage B. All patients were treated with RapidArc technique with flattening filter free (FFF) photon beams of 10MV from a TrueBeam linear accelerator. Technical, dosimetric and early clinical assessment was performed to characterize treatment and its potential outcome. Results: Median age was 68 years, median initial tumor volume was 124 cm(3) (range: 6-848). Median follow-up time was 7.4 months (range: 3-13). All patients completed treatment without interruption. Mean actuarial overall survival was of 9.6+/-0.9 months (95%C.L. 7.8-11.4), median survival was not reached; complete response was observed in 8/22 (36.4%) lesions; partial response in 7/22 (31.8%), stable disease in 6/22 (27.3%), 1/22 (4.4%) showed progression. Toxicity was mild with only 1 case of grade 3 RILD and all other types were not greater than grade 2. Concerning dosimetric data, Paddick conformity index was 0.98 +/- 0.02; gradient index was 3.82 +/- 0.93; V-95% to the clinical target volume was 93.6 +/- 7.7%. Mean dose to kidneys resulted lower than 3.0Gy; mean dose to stomach 4.5 +/- 3.0Gy; D-icm(3) to spinal cord was 8.2 +/- 4.5Gy; D-1% to the esophagus was 10.2 +/- 9.7Gy. Average beam on time resulted 0.7 +/- 0.2 minutes (range: 0.4-1.4) with the delivery of an average of 4.4 partial arcs (range: 3-6) of those 86% non-coplanar. Conclusions: Clinical results could suggest to introduce VMAT-RapidArc as an appropriate SBRT technique for patients with HCC in view of a prospective dose escalation trial.