Analysis of repeated proton beam therapy for patients with hepatocellular carcinoma

Abstract Purpose To evaluate the feasibility and efficacy of repeated proton beam therapy (PBT) and to analyze the dose–volume relationship. Patients and methods A retrospective analysis was performed in 83 patients who received definitive repeated PBT. Proton beams were delivered with expiratory gating. The numbers of treatment courses were 2, 3, and 4 in 68, 12, and 3 patients, respectively. MIM software was used for dose analysis. Results The planned median total dose was 70.5 GyE for all tumors and the median doses for the 1st, 2nd, 3rd and 4th treatments were 71.0, 70.0, 70.0, and 69.3 GyE, respectively. There was no severe acute toxicity, and no radiation-induced liver dysfunction (RILD) was observed. The median overall survival (OS) period from the first PBT was 61 months (95% CI: 50–71 months), and the 2- and 5-year OS rates were 87.5% (95%CI: 80.2–94.8%) and 49.4% (95%CI: 37.6–61.2%), respectively. The maximal delivered dose to the liver ranged from 66.7 to 248.1 GyE (mean: 124.93 GyE) and the mean liver dose ranged from 5.4 to 66.5 GyE (mean: 24.23 GyE). Conclusion Repeated PBT was well tolerated and safe, even though the liver doses in many patients deviated substantially from well-known critical levels for RILD.