Effects of Peptamen 1.6 in Malnourished Patients (or at Risk) With Pancreatic Neoplasia Undergoing Cephalic Pancreaticoduodenectomy (CPD): A Mechanistic Study

Inclusion Criteria: * Ambulatory patients who are malnourished or at risk of malnutrition, with a confirmed diagnosis of neoplasms of the periampullary region, pancreas, and duodenum, or pancreatic cancer, and who have undergone cephalic pancreaticoduodenectomy (CPD). * No prior neoadjuvant treatment (preoperative chemotherapy or radiotherapy): Patients must not have received neoadjuvant therapy as these treatments can affect metabolism, nutritional status, and gut microbiota, potentially interfering with the objectives of the study's nutritional intervention. Exclusion Criteria: * Refusal to sign informed consent: Informed consent is a mandatory requirement for study participation. Any patient unwilling to participate voluntarily will be excluded. * Patients who underwent surgery more than three months ago will be excluded, as the nutritional intervention must begin in the immediate postoperative period to adequately evaluate its impact on nutritional and metabolic status. * Presence of severe cardiac disease, nephropathy, or other severe comorbidities: Conditions such as severe cardiac disease, renal failure, or comorbidities that could induce malnutrition or impair the patient's ability to tolerate nutritional treatment will be exclusion criteria. These conditions may interfere with assessing the effects of nutritional supplementation in the context of pancreatic cancer treatment. * Diarrhoea associated with antibiotics, laxatives, or osmotically active agents: Diarrhoea caused by medications may alter nutrient absorption and affect tolerance to the nutritional supplement, potentially skewing results attributable solely to the nutritional intervention. * Treatment with other nutritional support: Patients receiving other oral nutritional supplement, enteral or parenteral nutrition will be excluded, as interactions with the studied formula could confound the efficacy results of the study's nutritional intervention. * Pregnancy or possibility of becoming pregnant. * Type 1 or Type 2 diabetes with HbA1c \>8%. * Galactosaemia, fructosaemia, or allergies to components of the nutritional supplement.