ctDNA Monitoring After Pancreatic Cancer Surgery (K-4CARE Lite Study)

Pancreatic ductal adenocarcinoma (PDAC) carries one of the worst prognoses among solid tumors. Even after curative-intent resection, 70-80% of patients recur within two years. Current post-operative surveillance relies on computed tomography (CT) imaging and the serum tumor marker CA 19-9, but both have limited sensitivity for detecting microscopic residual disease. This single-center, prospective observational study evaluates the use of the K-4CARE Lite platform-a tumor-informed plus tumor-agnostic circulating tumor DNA (ctDNA) assay with a limit of detection of 0.005%-for dynamic monitoring of minimal residual disease (MRD) in patients with resected PDAC. Thirty adult patients who have undergone R0 or R1 (margin \<1 mm) resection at Linkou Chang Gung Memorial Hospital will be enrolled over 24 months. Each participant will provide one baseline tumor tissue sample (formalin-fixed paraffin-embedded) and three serial blood samples at three pre-specified study timepoints: Timepoint 1 (Week 4 to Week 10 after surgery, before adjuvant chemotherapy); Timepoint 2 (12 weeks after Timepoint 1, approximately 3 months into adjuvant chemotherapy); and Timepoint 3 (at completion of adjuvant chemotherapy, approximately Month 6 after surgery). A fourth long-term follow-up phase (Timepoint 4) collects results from patient-funded ctDNA testing performed as part of routine care. The primary outcome is the cumulative MRD detection rate across the three pre-specified post-surgical timepoints (Timepoint 1, Timepoint 2, and Timepoint 3). Secondary outcomes include the association between ctDNA status and disease-free survival (DFS) and overall survival (OS), molecular clearance rate at Timepoint 3, lead time of molecular relapse over imaging, and platform performance. ctDNA results are reported back to the treating physician for reference but do not mandate treatment changes-all clinical decisions remain at the physician's discretion per standard guidelines. This study aims to genera