This study will examine how removal of part or all of the pancreas affects blood sugar control, metabolism, and clinical outcomes over time.

The study will include adults with diabetes before surgery who undergo pancreatic surgery as part of routine clinical care at Fondazione Policlinico Universitario A. Gemelli IRCCS.

Researchers will study whether glycemic control worsens after surgery and whether this risk changes according to the type of pancreatic resection. The study will also examine changes in glucose metabolism, and cancer-related outcomes.

Information from routine clinical care, metabolic tests, imaging, and pancreatic tissue samples collected during surgery may be used for research analyses.

Pancreatic surgery can lead to substantial changes in glucose metabolism because removal of pancreatic tissue reduces endocrine pancreatic mass and may affect insulin secretion, insulin sensitivity, and hormone regulation. In individuals with preoperative diabetes mellitus, pancreatic resection may further worsen glycemic control, increase treatment requirements, and contribute to heterogeneous metabolic trajectories after surgery.

This monocentric ambispective observational study will evaluate the clinical, metabolic, and oncological consequences of partial, near-total, and total pancreatectomy in adults with preoperative diabetes mellitus undergoing pancreatic surgery at Fondazione Policlinico Universitario A. Gemelli IRCCS.

The primary objective is to assess worsening of glycemic control 12 months after surgery according to the type of pancreatic resection. Secondary objectives include evaluation of longitudinal metabolic changes, diabetes treatment intensification, metabolic phenotypes before surgery, associations between preoperative metabolic characteristics and postoperative outcomes, and exploratory analyses of oncological outcomes including overall survival and disease-free survival.

The study integrates retrospective, ambispective, and prospective cohorts. Data collected as part of routine clinical care may include clinical and surgical information, laboratory data, imaging, oral glucose tolerance tests (OGTT), mixed meal tests (MMT), and metabolic clamp studies when available. Pancreatic tissue obtained from surgical specimens may also be used for histopathological, morphological, and molecular analyses to investigate relationships between pancreatic tissue characteristics, intrapancreatic fat, metabolic phenotypes, and clinical outcomes.

Inclusion Criteria:

• Adult patients (≥18 years)
• Diabetes mellitus at baseline
• Undergoing partial, near-total, or total pancreatectomy at the study center for benign or malignant pancreatic disease
• Availability of clinical and metabolic follow-up data according to study component
• Written informed consent for the ambispective and prospective components, where applicable

Exclusion Criteria:

• Age <18 years
• Absence of diabetes mellitus at baseline
• Missing essential clinical data or incomplete follow-up precluding evaluation of study outcomes
• Severe pre-existing non-oncologic clinical conditions with life expectancy <6 months
• Refusal, withdrawal, or inability to provide informed consent for the ambispective and prospective components, where applicable

Adult patients with diabetes mellitus at baseline undergoing partial, near-total, or total pancreatectomy according to routine clinical practice for benign or malignant pancreatic diseases at Fondazione Policlinico Universitario Agostino Gemelli IRCCS, including retrospective, ambispective, and prospective study components.

Data sharing plans have not yet been finalized. Any future sharing of de-identified individual participant data will be evaluated in accordance with institutional policies, ethical approvals, participant consent, and applicable data protection regulations.