1. Background Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies worldwide, with a 5-year survival rate below 10%. Systemic chemotherapy is the mainstay of treatment for the majority of patients who present with unresectable disease. However, the objective response rates for standard first-line regimens, such as nab-paclitaxel plus gemcitabine (AG) and FOLFIRINOX, are only 15-30%. Currently, there are no validated predictive biomarkers to guide chemotherapy selection, leading to a trial-and-error approach that exposes patients to unnecessary toxicity and delays effective treatment.

   Patient-derived organoids (PDOs) are three-dimensional in vitro models that recapitulate the genetic, histological, and phenotypic features of their source tumors. PDOs have shown promise as a functional precision medicine platform for predicting individual patient responses to anticancer therapies. Several retrospective and prospective studies across various tumor types have demonstrated high sensitivity and specificity for PDO-based drug sensitivity testing in predicting clinical outcomes. However, prospective data specifically focused on pancreatic cancer remain limited.

2. Study Objective The primary objective of this study is to evaluate the concordance between PDO-based drug sensitivity test results and clinical efficacy in PDAC patients receiving standard first-line chemotherapy. Secondary objectives include optimizing culture conditions and drug testing protocols for pancreatic cancer PDOs derived from surgical and biopsy specimens.

3. Study Design This is a prospective, observational, multicenter cohort study. The study will enroll treatment-naïve patients aged 18-75 years with histologically confirmed PDAC who are scheduled to receive first-line chemotherapy. Fresh tumor tissue will be obtained from routine surgical resection or biopsy procedures. PDOs will be established from the collected specimens and subjected to in vitro drug sensitivity testing against the corresponding chemotherapy regimens. The testing results will be classified as "sensitive" or "insensitive" based on IC50 values and maximum inhibition rates.

   Clinical treatment decisions will be made by the treating physicians according to standard guidelines and multidisciplinary team recommendations, independent of the PDO test results. Patients will be followed up every three treatment cycles with imaging assessments (CT or MRI) and laboratory evaluations. Clinical efficacy will be assessed using RECIST v1.1 criteria after six cycles or at the time of early surgery in the neoadjuvant setting. The concordance between PDO test results and clinical outcomes will be analyzed by calculating sensitivity, specificity, and overall accuracy.

4. Study Population Approximately 164 patients will be screened to achieve 80 evaluable cases, accounting for a PDO culture success rate of 85%, a follow-up rate of 90%, and exclusions due to non-PDAC pathology or non-first-line treatment regimens. Eligible patients must have adequate organ and bone marrow function, an ECOG performance status of 0-2, and a life expectancy of at least 3 months. Exclusion criteria include inadequate sample quality, PDO culture failure, pregnancy, severe comorbidities, and unstable medical conditions.

5. Study Sites This multicenter study is being conducted at six tertiary medical centers in China: Ruijin Hospital (Shanghai, lead site), Peking University Cancer Hospital, Beijing Friendship Hospital, The Second Hospital of Tianjin Medical University, The Second Xiangya Hospital of Central South University, and Shenzhen People's Hospital.

6. Risks and Benefits This observational study poses no additional physical risk to participants, as samples are collected from residual tissue during routine diagnostic or therapeutic procedures. No investigational interventions are administered. Participants will not receive direct medical benefit from study participation; however, the findings may contribute to the development of a clinically applicable predictive tool to guide chemotherapy selection for future pancreatic cancer patients, potentially improving treatment outcomes and quality of life.

7. Ethical Considerations The study will be conducted in accordance with the Declaration of Helsinki and applicable Chinese regulations. The protocol has been reviewed and approved by the institutional ethics committee. Written informed consent will be obtained from all participants prior to enrollment. All data will be anonymized and handled in strict compliance with privacy protection regulations.

8. Timeline The study is planned from February 2026 to February 2028.

Inclusion Criteria:

• Age 18-75 years, both sexes
• Pathologically confirmed pancreatic ductal adenocarcinoma (PDAC) in treatment-naïve patients
• Ability to obtain sufficient fresh tumor tissue samples for organoid establishment through surgery or biopsy
• Planned to receive neoadjuvant therapy for borderline resectable disease, conversion therapy for locally advanced disease, or first-line therapy for metastatic disease, using single-agent or combination chemotherapy
• At least one measurable lesion per RECIST 1.1 criteria
• ECOG performance status 0-2
• Life expectancy ≥3 months
• Adequate organ and bone marrow function: hemoglobin ≥9.0 g/dL; absolute neutrophil count ≥1.5×10⁹/L; platelet count ≥100×10⁹/L; total bilirubin ≤1.5×ULN (or ≤3×ULN with biliary obstruction); ALT/AST ≤2.5×ULN (or ≤5×ULN with biliary obstruction); serum creatinine ≤1.5×ULN or CrCl >60 mL/min
• Willing to sign informed consent, good compliance, and able to comply with follow-up

Exclusion Criteria:

• Sample quantity, quality, or preservation does not meet requirements
• Expected transport time >24 hours (including samples stored overnight before delivery)
• Organoid culture failure or testing quality control failure
• Inability to tolerate chemotherapy regimens
• Severe comorbidities, uncontrolled conditions, or active infections
• Pregnancy or breastfeeding
• History of severe autoimmune diseases
• Any unstable condition that may compromise patient safety or compliance
• Deemed unsuitable for inclusion by the investigator

The study population comprises treatment-naïve patients aged 18-75 years with histologically confirmed pancreatic ductal adenocarcinoma (PDAC) scheduled to receive first-line chemotherapy for borderline resectable, locally advanced, or metastatic disease. Eligible patients must have measurable disease per RECIST 1.1, ECOG performance status 0-2, life expectancy ≥3 months, and adequate organ function. Patients must provide sufficient fresh tumor tissue from surgery or biopsy (EUS-FNB 19G/22G) with tumor cell content and viability >50%. Approximately 164 patients will be screened to achieve 80 evaluable cases, accounting for follow-up rate of 90%, organoid culture success rate of 85%, and exclusions due to non-PDAC pathology or non-first-line treatment. All participants must sign informed consent and comply with follow-up.