Space-making particle therapy for unresectable hilar cholangiocarcinoma

Background: Although the primary treatment option for hilar cholangiocarcinoma (HC) has been surgical resection, most patients present with unresectable advanced tumors at the time of diagnosis. Particle therapy (PT) holds a great potential for HC, even though the anatomical proximity to the gastrointestinal tract prevents delivering a radical dose to the tumor. Space-making PT (SMPT), consisting of spacer placement surgery and subsequent PT, has been developed to minimize complications and maximize the therapeutic benefit of dose escalation for HC. This study aimed to conduct a dosimetric evaluation and examine the effectiveness of SMPT for the treatment of HC. Methods Between 2007 and 2018, 12 patients with unresectable HC treated with SMPT were enrolled. The treatment outcomes and effectiveness of spacer placement surgery were evaluated through analyses of pre- and post- surgical parameters of dose volume histograms. Results All patients completed the planned SMPT protocol. The median survival time was 29.6 months, and the 1- and 3-year overall survival rates were 82.5% and 45.8%, respectively. The mean V95% value (volume irradiated with 95% of the planned treatment dose) of the gross tumor volume and clinical target volume after spacer placement surgery improved to 98.5% and 96.6% from preoperative values of 85.6% and 78.1%, respectively ( p  = 0.0196 and p  = 0.0053 respectively). Grade 3 or higher adverse events after SMPT were seen in 6 patients. Conclusions SMPT led to improvements in dosimetric parameters and showed good feasibility and excellent outcomes. SMPT can be a promising novel alternative for unresectable HC.