Impact of Histopathological Response on Outcomes After Surgical Resection Following Carbon-Ion Radiotherapy for...

Carbon-ion radiotherapy (CIRT) provides superior dose distribution and higher biological effectiveness than conventional X-ray radiotherapy and has emerged as a promising component of multidisciplinary treatment for advanced pancreatic ductal adenocarcinoma (PDAC). However, evidence regarding surgical resection after CIRT remains limited. In this study, we aimed to evaluate the feasibility, histopathological therapeutic response, and oncological outcomes of pancreatic resection after CIRT-based multimodal treatment.

We retrospectively analyzed 12 patients with borderline resectable pancreatic cancer with arterial involvement (BR-A) or unresectable locally advanced PDAC (UR-LA), who underwent surgical resection following CIRT at our institution between January 2016 and June 2025. The surgical outcomes, perioperative morbidity, pathological therapeutic responses, and survival outcomes were assessed.

Surgical resection after CIRT was feasible in all patients. The procedures included pancreaticoduodenectomy (n = 5), distal pancreatectomy (n = 2), and distal pancreatectomy with celiac axis resection (n = 5). R0 resection was achieved in 11 patients (92%) and no pathological lymph node metastasis was identified. A marked histopathological response (Evans Grades III-IV) was observed in 83% of patients. No local recurrences were observed in the CIRT irradiation field. The 3-year progression-free survival and overall survival (OS) rates calculated from treatment initiation were 74.1% and 79.5%, respectively, whereas the corresponding 3-year recurrence-free survival and OS rates calculated from surgical resection were 47.6% and 50.8%, respectively.

Surgical resection following CIRT-based multimodal treatment is feasible and safe, achieving a favorable histopathological response and durable local control in selected patients with PDAC with arterial involvement.