A novel technique of spacer implantation and proton beam therapy for hilar cholangiocarcinoma: a case report.

The primary treatment for hilar cholangiocarcinoma is a surgical resection. However, most patients have already lost the opportunity for surgical treatment at the time of the initial diagnosis. Photon therapy (X-ray) has limited efficacy, whereas proton beam therapy (PBT) can improve local control. However, when tumors are located near the gastrointestinal tract, the therapeutic effect remains limited. Space-making particle therapy (SMPT) has emerged as a strategy to address the clinical challenge of high-dose radiation exposure to nearby organs at risk (OARs). This technique involves the surgical implantation of a bioabsorbable spacer prior to particle therapy delivery. Therefore, we are interested in the use of SMPT to preserve the gastrointestinal tract. A 77-year-old man with hilar cholangiocarcinoma underwent placement of a bioabsorbable spacer and then received radical PBT of 72.6 Gy (relative biological effectiveness, RBE) in 22 fractions. Surgery was not included in the original treatment plan. However, approximately 5 months after completing PBT, the patient developed biliary fluid accumulation, which subsequently required surgical intervention. Notably, pathological examination of the resected irradiated field revealed a complete pathological response (pCR), providing direct evidence of the treatment efficacy. This report describes one of the first cases in which a bioabsorbable spacer was surgically placed to preserve the gastrointestinal tract during PBT. SMPT is an innovative solution for hilar cholangiocarcinoma adjacent to the gastrointestinal tract. This case demonstrated the early feasibility and short-term efficacy of SMPT, but long-term follow-up is needed.