Clinical Outcomes of Patients With Unresectable Cholangiocarcinoma Treated With Proton Beam Therapy

Objective: To investigate the clinical outcomes and failure patterns of patients with unresectable cholangiocarcinoma (CC) who had been treated with proton beam therapy (PBT). Methods: The authors retrospectively examined 30 patients with unresectable CC who had undergone PBT between November 2015 and December 2017. Survival curves were plotted with the Kaplan-Meier method. Independent predictors of survival were identified by multivariate Cox proportional hazard regression analyses. Complications were assessed using the Common Terminology Criteria for Adverse Events v4.0. Results: The median tumor size was 7 cm. Seventeen patients (56.7%) had regional lymph node metastases. The median radiation dose was 72.6 cobalt gray equivalents, and 23 patients (76.7%) received concurrent chemotherapy. The 1-year local control, regional control, and distant metastases-free rates were 88%, 86%, and 68%, respectively. The median overall survival and progression-free survival were 19.3 and 10.4 months, respectively. The median jaundice-free survival was 13 months, with a 1-year biliary tract infection (BTI)-free rate of 58%. Patients who received concurrent chemotherapy had a better median progression-free survival (12.1 vs. 4.7 mo). The most common form of acute toxicity from PBT was acute skin reactions which were rarely severe (grade III: 7% of patients). Three and 2 patients had grade III-IV toxicities and radiation-induced liver disease. There were no deaths caused by PBT or concurrent chemotherapy. Conclusions: PBT is clinically useful in patients with unresectable CC, even in the presence of large tumors or regional nodal metastases. Its use may induce durable symptom relief, without increasing acute or late toxicity.