The goal of this real-world study is to learn if maintenance chemotherapy with Tegafur, Gimeracil, and Oteracil Potassium (S-1) can improve disease-free survival (DFS) compared to follow-up observation in patients with resected pancreatic cancer at high risk of recurrence or metastasis after adjuvant therapy. The main questions it aims to answer are:
* Does maintenance therapy with S-1 improve disease-free survival (DFS) compared to follow-up observation after standard treatment for resected high-risk pancreatic cancer? * Does S-1 maintenance therapy improve overall survival (OS), distant disease-free survival (DDFS), and local recurrence-free survival (LRFS) compared to observation? * What are the safety and tolerability profiles of S-1 maintenance therapy compared to observation? Researchers will compare two groups: the S-1 maintenance therapy group and the observation-only group, to see if S-1 improves survival outcomes and safety.
Participants will:
* Receive maintenance chemotherapy with S-1 based on body surface area dosing or be assigned to the observation group without drug intervention. * Undergo imaging evaluations every 12 weeks to monitor for disease recurrence or metastasis. * Report side effects and any adverse events during the study.
Histologically confirmed pancreatic cancer (originating from the pancreatic ductal epithelium);
Meets one of the following conditions: Pathologically confirmed as moderately differentiated, moderately to poorly differentiated, or poorly differentiated; or pathologic staging as: T3N0M0, T1-3N1-2M0, T4N0-2M0; or one or more surgical margins are R1 resected (R0 resection if no tumor cells are found more than 1mm from the margin, otherwise R1 resection); or involvement of the portal vein and/or superior mesenteric vein resection; or pre-adjuvant chemotherapy CA19-9 > 90 U/mL; or pre-adjuvant chemotherapy ctDNA testing positive;
Completed standard treatment: Received radical resection, postoperative adjuvant therapy (including adjuvant chemotherapy based on gemcitabine or fluorouracil), and radiotherapy (if applicable);
Eligible for oral medication;
Pancreatic cancer originating from non-pancreatic ductal epithelium, including pancreatic neuroendocrine tumors, pancreatic acinar cell carcinoma, pancreatoblastoma, and solid-pseudopapillary tumor;
Incomplete macroscopic resection (R2 resection);
Presence of distant metastasis (including malignant ascites and pleural effusion, peritoneal metastasis) or locally recurrent pancreatic cancer;
CA19-9 > 180 U/mL within 21 days before enrollment;