Phase I Dose-Escalation Study of Proton Beam Therapy for Inoperable Hepatocellular Carcinoma

PURPOSE: 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 considered eligible for PBT. Patients received PBT with 60 GyE in 20 fractions (dose level 1; equivalent dose in 2 Gy fractions [EQD2], 65 GyE(10)); 66 GyE in 22 fractions (dose level 2; EQD2, 71.5 GyE(10)); or 72 GyE in 24 fractions (dose level 3; EQD2, 78 GyE(10)). 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 GyE(10) should be delivered for achievement of local tumor control.