The aim of this study is to investigate the clinical efficacy and safety of ablative carbon ion radiotherapy for locally advanced unresectable pancreatic cancer with pencil beam scanning and simultaneous integrated boost (SIB) technology.

The aim of this study is to investigate the clinical efficacy and safety of ablative carbon ion radiotherapy for locally advanced unresectable pancreatic cancer using pencil beam scanning and simultaneous integrated boost technology with respect to toxicity and tumor control. All enrolled patients will receive carbon ion radiotherapy for the primary pancreatic lesions, positive lymph nodes, and retroperitoneal high-risk recurrence areas. The prescription dose for primary pancreatic lesion, positive lymph node, and retroperitoneal high-risk recurrence area is 67.5 Gy (RBE weighted dose) in 15 fractions for 3 weeks; Pancreatic primary lesion and positive lymph node SIB to 75 Gy (RBE weighted dose) in 15 fractions for 3 weeks. The primary endpoint is 2-year cumulative local regional progression rate (LRP), and the secondary endpoint is to assess the overall survival (OS) and toxicities. Toxicity was assessed using the Common Adverse Event Evaluation Criteria (CTCAE) Version 5.0, and safety and toxicity will be assessed by clinical examination, laboratory examination, and imaging (including CT, MRI, and/or PET/CT).

Inclusion Criteria:

1. Have the ability to sign the written informed consent;
2. Ductal adenocarcinoma of the pancreas confirmed by histopathology or cytopathology;
3. Distant metastasis was excluded by imaging assessment (PET-CT, cranial MRI), and was defined as locally advanced unresectable according to NCCN Guidelines Version 2022.1, that is, T4N0-2M0, Stage III (AJCC/UICC Version 8);
4. The maximum diameter of pancreatic primary lesion and positive lymph node ≤7cm;
5. Pancreas primary lesion or positive lymph node did not invade digestive tract (stomach, duodenum and small intestine);
6. Eastern Cooperative Oncology Group (ECOG) performance score 0-1;
7. Adequate bone marrow function (neutrophil count ≥1.5×109/L, platelet count ≥100×109/L, hemoglobin ≥10.0g/dL);
8. Adequate liver function (total bilirubin <1.5 times the upper limit of normal value, aminotransferase <2.5 times the upper limit of normal value);
9. Adequate renal function (serum creatinine <2mg/dL, or creatinine clearance >50mL/min).

Exclusion Criteria:

1. Multiple primary pancreatic lesions (>1);
2. Tumor invaded the adjacent digestive tract;
3. Radiation therapy history;
4. Other local treatments history for pancreatic cancer, such as HIFU and irreversible electroporation;
5. The irradiation dose of organs at risk cannot reach the dose constraint;
6. Other malignant tumors history;
7. Inability to understand the purpose of treatment or unwillingness/inability to sign informed consent.