Proton beam radiotherapy vs. radiofrequency ablation for recurrent hepatocellular carcinoma: A randomized phase III trial

Background & Aims: Proton beam radiotherapy (PBT) has recently been applied to treat hepatocellular carcinoma (HCC); however, there is no randomized controlled trial-based evidence on its safety and efficacy. We compared the outcomes of PBT and radiofrequency ablation (RFA) in patients with recurrent/residual HCC (rHCC) in a phase III non-inferiority trial. Methods: Patients with rHCC (size <3 cm, number <-2) were randomly assigned to receive PBT or RFA according to Child-Pugh score and tumor stage. After randomization, if the assigned treatment was technically infeasible, crossover was allowed. The primary endpoint was 2-year local progression-free survival (LPFS), with a non-inferiority margin of 15% in the per-protocol (PP) population; a complementary analysis was performed in the intention-to-treat (ITT) population (NCT01963429). Results: The ITT population comprised 144 patients receiving either PBT (n = 72) or RFA (n = 72). Six patients switched from the PBT arm to the RFA arm and 19 patients switched from the RFA arm to the PBT arm. In the PP population, the 2-year LPFS rate with PBT (n = 80) vs. RFA (n = 56) was 94.8% vs. 83.9%, a difference of 10.9 percentage points (90% CI 1.8-20.0; p < 0.001); in the ITT population, the 2-year LPFS rate with PBT vs. RFA was 92.8% vs. 83.2%, a difference of 9.6 percentage points (90% CI 0.7-18.4; p < 0.001), meeting the criteria for non-inferiority. The 3- and 4 year LPFS rates for PBT were also non-inferior to those for RFA. The most common adverse events were radiation pneumonitis (32.5%) and decreased leukocyte counts (23.8%) for PBT and increased alanine aminotransferase levels (96.4%) and abdominal pain (30.4%) for RFA. No Grade 4 adverse events or mortality were noted. Conclusions: PBT showed LPFS values that were non-inferior to those for RFA; in addition, PBT was tolerable and safe. Lay summary: Radiofrequency ablation is the standard of care for patients with small hepatocellular carcinoma in whom surgery is not feasible. This study is the first phase III randomized controlled trial to evaluate the clinical outcomes of proton beam radiotherapy vs. radiofrequency ablation in patients with recurrent small HCC. Our findings show that this new technique is not inferior and can be applied safely in patients with small recurrent hepatocellular carcinoma. (C) 2020 European Association for the Study of the Liver. Published by Elsevier B.V.