licenses/by-nc/3.0/)which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Open Access Phase I Dose-Escalation Study of Proton Beam Therapy for Inoperable Hepatocellular C

The purpose of this study is to determine the optimal dose of proton beam therapy (PBT) in hepatocellular carcinoma (HCC) patients. Materials and Methods Inoperable HCC patients who had naïve, recurrent, or residual tumor to treatment were con-sidered eligible for PBT. Patients received PBT with 60 GyE in 20 fractions (dose level 1; equivalent dose in 2 Gy fractions [EQD2], 65 GyE10); 66 GyE in 22 fractions (dose level 2; EQD2, 71.5 GyE10); or 72 GyE in 24 fractions (dose level 3; EQD2, 78 GyE10). Dose-limiting toxicity was determined by grade ≥ 3 acute toxicity. Results Twenty-seven patients were enrolled; eight, seven, and 12 patients were treated with dose levels 1, 2, and 3, respectively. Overall, treatment was well tolerated, with no dose-limiting toxicities. The complete response (CR) rates of primary tumors after PBT for dose levels 1, 2, and 3 were 62.5 % (5/8), 57.1 % (4/7), and 100 % (12/12), respectively (p=0.039). The 3- and 5-year local progression-free survival (LPFS) rates among 26 patients, excluding one patient who underwent liver transplantation after PBT due to its probable significant effect on disease control, were 79.9 % and 63.9%, respectively, and the 3- and 5-year overall survival rates were 56.4 % and 42.3%, respectively. The 3-year LPFS rate was significantly higher in patients who achieved CR than in those who did not (90 % vs. 40%, p=0.003). Conclusion PBT is safe and effective and an EQD2 ≥ 78 GyE10 should be delivered for achievement of local tumor control. Key words Hepatocellular carcinoma, Proton therapy, Radiotherap