Short-term relapse and poor survival are prevalent in patients with pancreatic adenocarcinoma (PAAD) after surgeries. Despite the importance of adjuvant treatments for resected PAAD patients, there is currently no suitable biomarker to identify those individuals with high risk of recurrence and inform therapeutic decision making. In this study, we aim to examine whether postoperative circulating tumor DNA (ctDNA) could be used as a biomarker for early detection of minimal residual disease (MRD) and predicting relapse in resected PAAD through high-depth targeted next-generation sequencing.

Inclusion Criteria:

• Pathologically diagnosed pancreatic adenocarcinoma (stage I-III)
• KRAS mutations identified in resected tumor tissues
• Margin negative (R0) or no imaging recurrence/metastasis and CA 19-9<37 U/ml in postoperative 4-8 weeks (before adjuvant chemotherapy)
• Receiving adjuvant chemotherapy
• ECOG 0-2
• Signed informed consent

Exclusion Criteria:

• With serious internal medicine diseases, infectious diseases, other solid tumors (except PAAD) or hematologic disorders
• Distant organ metastasis or malignant ascites
• Receiving neo-adjuvant therapy before surgery
• Imaging recurrence/metastasis or CA 19-9>37 U/ml in postoperative 4-8 weeks (before adjuvant chemotherapy)
• Pregnant or breastfeeding at time of enrollment
• Prior transplantation of bone marrow, stem cell or organ

The pathologically diagnosed stage I-III PAAD patients who underwent resections carried KRAS mutations in tumor tissues. Margin negative (R0) or no imaging recurrence/metastasis and CA 19-9<37 U/ml in postoperative 4-8 weeks (before adjuvant chemotherapy).