The overall objective of this study is to confirm that ctDNA detected after curative intended treatment for PDAC is a marker of residual disease and for risk-of-recurrence, and applicable in clinical practice.

Primary objective To confirm that ctDNA analyses performed after PDAC treatment can identify patients with a high risk-of-recurrence.

Specifically, we want to determine the association between disease-free survival (DFS) and ctDNA detection status after (1) curative-intended surgery and (2) adjuvant chemotherapy.

The study will prospectively enroll patients who undergo potentially curative surgery for PDAC. The intervention is repeated blood sampling at pre-defined time points.

Patient identification Patients with PDAC are screened for eligibility by the involved physicians based on the protocol of the multidisciplinary tumor board (MDT). The screening will be done based on the electronic health record in the electronic journal (at present, for example, Take Care). The National Health Record may be accessed for some patients to complete the record.

Patient recruitment and informed consent The involved physicians screen patients meeting the inclusion criteria specified below. Eligible patients are approached in person or initially by phone, after they have been informed about the diagnosis and the planned surgery. Patients are given written and oral information about the project by a trained research nurse or by an involved physician. Informed consent will be obtained before the beginning of any study-related procedures.

The signed and dated consent forms are scanned into the project's electronic database and stored physically in a locked space.

Inclusion Criteria:

• Pancreatic ductal adenocarcinoma, according to the assessment of the MDT.
• Age 18 years or older.
• Patient able to understand and sign written informed consent in Swedish.
• Scheduled for curative intent surgical resection.

Exclusion Criteria:

• Hereditary pancreatic cancer.
• Verified distant metastases.
• Patients who are unlikely to comply with the protocol (e.g. uncooperative attitude), inability to return for subsequent visits and/or otherwise considered by the Investigator to be unlikely to complete the study.
• Other cancers (excluding prior pancreatic cancer or skin cancer other than melanoma) within 3 years from eligibility screening.

Patients with histologically verified pancreatic adenocarcinoma (from surgically removed tumour tissue = ground truth) regardless of their ability to receive SOC adjuvant chemotherapy or not (observation only - due to pre-existing medical conditions), regardless of type of chemotherapy.

After completion of the study, the SAB and study group to decide whether to share the results on a group level, i.e. anonymously