Selection of Proper Modality in Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma

BACKGROUND/AIMS: As the optimal stereotactic body radiation therapy (SBRT) modality for hepatocellular carcinoma (HCC) has not been confirmed, we aimed herein to provide a practical guideline by our retrospective review. METHODS: Thirty-nine patients with primary HCC who underwent liver SBRT via 3 modalities (helical tomotherapy [HT]: 22, volumetric modulated arc therapy [VMAT]: 13, Cyberknife: 4) at our institution between July 2014 and July 2015 were included. Modalities were compared with regard to dose conformity index (CI), homogeneity index (HI), clinical results, and patient compliance. RESULTS: VMAT SBRT had favorable conformity (CI: 0.7±0.2), homogeneity (HI: 1.1±0.0), and shortest treatment time (100.2±26.1 seconds). HT SBRT yielded good dosimetric outcomes, especially in conformity (CI: 1.0±0.2). Although the Cyberknife SBRT synchrony system allowed real-time tumor targeting, the treatment time was longest (3,015.0±447.3 seconds), invasive pre-treatment procedures were required, and the HI (1.3±0.0) was lowest. CONCLUSIONS: All 3 modalities yielded competent dosimetric planning parameters. VMAT SBRT was most appropriate for tumors with residual lipiodol or patients with poor conditions. HT SBRT is available for multiple or irregular targets. Cyberknife SBRT is recommended for carefully selected patients and tumors indicated for sono-guided fiducial insertion.

Re-Irradiation of Hepatocellular Carcinoma: Clinical Applicability of Deformable Image Registration

PURPOSE: This study aimed to evaluate whether the deformable image registration (DIR) method is clinically applicable to the safe delivery of re-irradiation in hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Between August 2010 and March 2012, 12 eligible HCC patients received re-irradiation using helical tomotherapy. The median total prescribed radiation doses at first irradiation and re-irradiation were 50 Gy (range, 36-60 Gy) and 50 Gy (range, 36-58.42 Gy), respectively. Most re-irradiation therapies (11 of 12) were administered to previously irradiated or marginal areas. Dose summation results were reproduced using DIR by rigid and deformable registration methods, and doses of organs-at-risk (OARs) were evaluated. Treatment outcomes were also assessed. RESULTS: Thirty-six dose summation indices were obtained for three OARs (bowel, duodenum, and stomach doses in each patient). There was no statistical difference between the two different types of DIR methods (rigid and deformable) in terms of calculated summation operatorD (0.1 cc, 1 cc, 2 cc, and max) in each OAR. The median total mean remaining liver doses (M(RLD)) in rigid- and deformable-type registration were not statistically different for all cohorts (p=0.248), although a large difference in M(RLD) was observed when there was a significant difference in spatial liver volume change between radiation intervals. One duodenal ulcer perforation developed 20 months after re-irradiation. CONCLUSION: Although current dose summation algorithms and uncertainties do not warrant accurate dosimetric results, OARs-based DIR dose summation can be usefully utilized in the re-irradiation of HCC. Appropriate cohort selection, watchful interpretation, and selective use of DIR methods are crucial to enhance the radio-therapeutic ratio.