WS4-3 - Current status and future prospects of stereotactic body radiotherapy for liver malignancies

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Stereotactic body radiotherapy (SBRT) for liver malignancies is curative and safe treatment, but the definitive evidence is still lacking. In our institution, we reported high local control (3-year local control rate: 96%) and feasibility in prospective phase II study of SBRT for solitary HCC (≤4 cm) (Cancer 2016; 122: 2041-9). In addition, SBRT has specific characteristics; those are 1. Non-invasive therapy without pain or hemorrhage, 2. Easy to treat deep lesion in the body, 3.Little complication in relation with large vessel or biliary tract when treating those adjacent tumors, 4. Flexible dose strength based on the liver function and target volume. Because of those characteristics, we believe that SBRT plays an important role in the treatment for HCC, especially adjacent to or invading large vessel and just beneath diaphragm. Currently, in order to validate the efficacy and feasibility of SBRT for HCC, multicenter prospective study of SBRT for untreated solitary HCC (STRSPH study; UMIN000013011) is ongoing. Liver oligometastasis from colorectal cancer (OMCRC) is another disease that SBRT can play an important role. Although colorectal cancer is rather radio-resistant, we believe that SBRT can treat patients with OMCRC and result in good local control with feasibility. In fact, we reported excellent outcomes of SBRT for pulmonary and liver OMCRC with a total dose of 50-60 Gy in five fractions prescribed to the 60% isodose line of the maximum dose covering the surface of the planning target volume. The local control was 100% (J Radiat Res. 2016; 57: 400-5). Currently, in order to validate the efficacy and feasibility of SBRT for OMCRC, single institution prospective study of SBRT for OMCRC (UMIN000026577) is ongoing. We think radiation oncologists should show the efficacy and feasibility of SBRT for liver malignancies to let many clinician and patients understand SBRT.