Role of Particle Beam Therapy for Extrahepatic Biliary Cancer—Updated Systematic Review and Meta‐Analysis for Comparison Between Photon and Particle Radiotherapy

BACKGROUND/PURPOSE: The study was designed to examine the role of particle beam therapy (PT) in the treatment of extrahepatic biliary cancer (EHC). METHODS: We conducted a systematic review and meta-analysis to compare the outcomes of PT and photon radiotherapy in treating EHC. Medline/PubMed and Japan Medical Abstracts databases were screened using a systematic search strategy. The primary endpoint was overall survival (OS), pooled using a random effects model. RESULTS: In total, 236 articles were retrieved. After screening, 11 articles were retained, comprising 2108 patients (nine photon articles, n = 2038 patients; two PT articles, n = 70 patients). We have updated and incorporated the outcomes of the prospective data registry (Proton-net, n = 137 patients) for PT. The 1-year OS probability rates were 56% (95% confidence interval = 49%-62%) for the photon and 72% (65%-78%) for the PT groups (p < 0.001). The median survival time was 13.1 months (11.0-15.1 months) for the photon group and 18.8 months (14.1-23.4 months) for the PT group (p = 0.03). The PT group demonstrated a superior OS rate compared to that observed in the photon group. The incidence rates of grade 3 ≤ toxicity was 18.5%-33% in the photon radiotherapy group and 2.9%-15% in the PT group. CONCLUSION: PT demonstrated superior outcomes with acceptable toxicity compared to those noted with photon radiotherapy for EHC in this meta-analysis. In the absence of randomized trials, this meta-analysis provides useful evidence that PT can be considered an effective therapeutic modality for EHC.