The goal of this observational study is to explore whether contrast-enhanced ultrasound (CEUS) can early predict and evaluate the treatment response of first-line chemotherapy in locally advanced and borderline resectable pancreatic cancers.

The main questions it aims to answer are:

Question 1: What quantitative parameters of CEUS performed before first-line chemotherapy can predict the early treatment response of patients with locally pancreatic cancer?Question 2: Can CEUS reflect early neovascular changes after first-line chemotherapy in pancreatic tumors? Participants will receive CEUS examination carried out by experienced operators before the first cycle of chemotherapy and after 2 treatment cycles.

Pancreatic cancer is a highly fatal disease with a low 5-year survival rate of approximately 9% in the United States. Due to vague symptoms and early involvement of vessels, surgical treatment is only feasible for 20% of patients. First-line chemotherapy, which can improve the rate of R0 resection, is increasingly being used and is preferred in the ASCO guidelines for patients with locally advanced and borderline resectable pancreatic cancers. Early prediction and evaluation of the treatment response can provide prognostic information and enable oncologists to tailor therapeutic strategies.

Contrast-enhanced ultrasound (CEUS) is of interest for its ability to gain macrovascular and microvascular information about organs and to aid our understanding of the complexity of angiogenesis in different types of tumors. CEUS is a quantitative kinetic imaging modality that can assess intravascular blood flow in pancreatic tumors even at the capillary level. Our previous studies have confirmed that the enhancement patterns of CEUS in pancreatic ductal adenocarcinoma (PDAC) have correlation with the overall survival time. Now we hypothesize that the enhancement patterns before first-line chemotherapy can predict the treatment response and the changes in the pharmacokinetics of contrast material after treatment would reflect early neovascular changes in pancreatic tumors.

The investigators plan to recruit patients who are about to receive first-line chemotherapy for pathologically diagnosed PDAC from the department of General Surgery and Medical Oncology of our hospital. The patients will receive CEUS examination before the first cycle of chemotherapy and after 2 treatment cycles. Quantitative perfusion analysis will be performed by experienced radiologists and artificial intelligence for all of the images. According to the published literature, clinical response in patients were evaluated based on the Response Evaluation Criteria in Solid Tumors (RECIST, version 1.1) combined with the changes of serum levels of CA 19-9. Changes of CEUS quantitative perfusion parameters will be compared to clinical measurement of response to treatment taking into consideration standard response criteria including radiological imaging, serum CA 19-9 levels and repeat pathology as applicable

Inclusion Criteria:

• The main inclusion criteria were histologically proven pancreatic ductal adenocarcinoma and medical fitness for first-line chemotherapy Patients were consent to receive examinations of contrast enhanced ultrasound

Exclusion Criteria:

• Patients with distal metastases or patients refusing chemotherapy Patients who were not suitable for contrast-enhanced ultrasound ,such as pregnant or lactating women Patients without complete clinical data

The patients were diagnosed as pancreatic ductal adenocarcinoma pathologically and planned to receive first-line chemotherapy. The patients could receive regular follow up.