The majority patients diagnosed with pancreatic cancer have metastatic disease at the time of diagnosis. The prognosis is extremely poor with a 5-year survival rate of less than 5%. Treatment with chemotherapy can improve efficacy, but still the median progression-free survival in patients receiving nab-paclitaxel and gemcitabine is only 5,5 months and median overall survival is less than one year. There is a urgent need for tools for predicting the efficacy of the treatment. The current trial aims at investigating the biomarker potential of circulating tumor cells (CTCs) in metastatic pancreatic cancer patients treated by gemcitabine and nab-paclitaxel.

Inclusion Criteria:

• Male or female > 18 years up to 80 years
• Histologically or cytologically proven adenocarcinoma of the pancreas before start of treatment. Also patients for whom there is a strong suspicion of unresectable pancreatic cancer will before the diagnosis is confirmed be asked for consent to take 2 additional biopsies at the time of diagnostic biopsy retrieval, in case the histological analysis confirms that they can be included.
• Locally advanced (primarily unresectable) and/or metastatic disease.
• Presence of at least one measurable lesion according to the RECIST criteria, not restricted to previously irradiated area or limited to bone, pleural effusion or ascites.
• ECOG/WHO performance status ≤2
• Absolute neutrophil count (ANC) >1.5 x 109 /L and platelet count >100 x 109/L
• Total bilirubin < 1.5 times the upper limit of the normal range at the institution (ULN) or AST or ALT < 2 x ULN. If liver metastases are present, patients can be included if total bilirubin < 5× ULN or AST/ALT <10× ULN. Dose reductions of paclitaxel will be performed when bilirubin >2xULN, depending on increase of the bilirubin level according to the recommendations of the Summary of Product Characteristics.
• Serum creatinin < 1,5 ULN / calculated creatine clearance > 60 ml/min.
• Written informed consent

Exclusion Criteria:

• Current infection, bowel obstruction or subobstruction, or other uncontrolled intercurrent illness.
• Prior medical treatment for advanced pancreatic cancer
• Confirmed brain metastasis.
• Concurrent or past history of another malignancy except curatively treated non-melanoma skin cancer or in situ carcinoma of the cervix.
• Treatment with any other investigational drug more than 30 days prior to study entry.
• Allergy to anyone of the included drugs.
• Female patient breast feeding or pregnancy
• Not able/ or not willing to use adequate contraception (defined below). A pregnancy test will be included in the baseline visit for women of childbearing potential.