The goal of this interventional study is to learn about the efficacy of first-line chemotherapy with Gemcitabine in metastatic pancreatic adenocarcinoma patients expressing the GemCore signature in their tumor. The main question it aims to answer is to assess efficacy of Gemcitabine (tumor response, survival rate) in the population of patient bearing the GemCore signature.

Participants will start the chemotherapy with Gemcitabine as usually performed in standard care of their center. They will consent to a genomic analyze of their tumor to know if it bears the GemCore signature. The center will manage the participant's follow up as usually realized in standard care.

Inclusion Criteria:

• Metastatic pancreatic adenocarcinoma histological proved
• FOLFIRINOX chemotherapy-ineligible patient and going to receive first-line metastatic chemotherapy with gemcitabine monotherapy
• Tumor material allowing assessment of GEMCore status (i.e. FFPE block with tumor cellularity ≥ 10%);
• Life expectancy > 2 months;
• Measurable target according to RECIST 1.1 criteria;
• No previous treatment in metastatic situation;
• Age ≥ 18 years;
• Patient not opposed to study participation;
• Affiliation to a social security system, or beneficiary of such a scheme.

Exclusion Criteria:

• Contraindication to Gemcitabine treatment;
• ECOG performance status ≥ 3;
• Person in emergency situation or unable to express non-opposition;
• Patient under a legal protection measure (adult under guardianship, curatorship or safeguard of justice);
• Unable to undergo medical follow-up for geographical, social or psychological reasons.