Gastrinoma and Zollinger-Ellison Syndrome

Michael D. Smith, MD
The Operative Review of Surgery. 2023; 1:168-174.

Table of Contents

Pathophysiology

Definitions

  • Gastrinoma: Gastrin Secreting Neuroendocrine Tumor 1
  • Zollinger-Ellison Syndrome (ZES): Syndrome of Gastric Acid Hypersecretion Due to Gastrinoma 2

Distribution

  • Duodenum – Most Common Location 1,3
    • Sporadic Tumors: 50-88%
    • MEN-1-Associated Tumors: 70-100%
    • *Most Common in the First Portion
  • Pancreas: 20-25% 4
  • Other: 5-15% 1,5-7
    • Stomach
    • Jejunum
    • Liver
    • Biliary Tract
    • Peripancreatic Lymph Nodes
    • Ovary

Gastrinoma (Passaro) Triangle

  • Contain 60-90% of Tumors 9,10
  • Borders:
    • Junction of the Cystic & Common Bile Ducts
    • Junction of the Second & Third Portions of the Duodenum
    • Junction of the Neck & Body of the Pancreas

Size and Malignancy

  • Duodenal Tumors: 4,10
    • Usually Small in Size (< 1 cm) (60-90%)
    • Liver Metastases are Uncommon (5%)
  • Pancreatic Tumors: 4,10
    • Usually Large (≥ 3 cm) (70%)
    • Liver Metastases are Common (52%)
  • Over Half Are Malignant (60-90%) at the Time of Diagnosis 10-12
  • 20-30% are Associated with Multiple Endocrine Neoplasia Type 1 (MEN1) 3,13
    • Most Common PNET in MEN-1 Syndrome 14

Epidemiology

  • Average Age: 40 4
  • 55-56% are Male 4

Gastrinoma (Passaro) Triangle 8

Presentation

Peptic Ulcer Disease

  • Incidence: 73-98% 3,10
  • The Most Common Presenting Symptom
  • Due to Significantly Increased Basal Acid Output (BAO)
    • Typically 4-Fold Higher, Can Be Over 10-Fold Higher 10
  • Associated Symptoms:
    • Abdominal Pain
    • Bleeding
    • Stricture
    • Fistula
    • Perforation
  • Often Severe and Refractory to Initial Management with Proton Pump Inhibitors
  • Ulcer Location: 15
    • Proximal Duodenum: 75% – Most Common
    • Distal Duodenum: 14%
    • Jejunum: 11%
    • *Often Occur More Distal in the Duodenum/Jejunum than Sporadic Ulcers
  • Associated with Prominent Gastric Folds (94%) with Gastric Enterochromaffin-Like (ECL) Cell Hyperplasia 10

Additional Symptoms 3,10

  • Heart Burn (52-55%)
  • Diarrhea (60-75%)
  • Weight Loss (7-53%)
  • Nausea and Vomiting (20-30%)

Diagnosis

Diagnosis

  • Diagnosis is Frequently Delayed 4-7 Years Because ZES is Such an Uncommon Cause of PUD 16-18
  • Initial Screening: Elevated Fasting Serum Gastrin (FSG) and Measurement of Gastric pH 3,17,18
  • Additional Testing if Initial Findings are Not Diagnostic:
    • Secretin Stimulation Test
      • Secretin Normally Shows Minimal Change but Induces a Marked Gastrin Increase in ZES
    • Fasting Gastric Basal Acid Output (BAO) – Historical and Now Rarely Performed 3,19
  • Diagnostic Criteria: 10
    • FSG > 10x Upper Limit of Normal and Gastric pH ≤ 2
    • FSG < 10x Upper Limit of Normal and Secretin Stimulation Test Positive (≥ 120 pg/ml Increase)
    • FSG < 10x Upper Limit of Normal and Elevated BAO (> 15 mEq/hr)
  • Gastrin Measurement Requires Holding Any PPI for 3-7 Days Before Testing (PPIs Induce Hypergastrinemia) 20
  • If Unsafe to Hold PPI (Life-Threatening Bleeding, etc.): Consider Somatostatin Receptor Imaging for Diagnosis & Localization

TNM Staging

Localization

  • Initial Imaging: Noninvasive (CT or MRI)
  • Somatostatin Receptor Imaging 22,23
    • Consider if Initial Imaging Fails to Localize
    • Options:
      • Somatostatin (Octreotide) Receptor Scintigraphy (SRS) – Classic Test Used
      • Functional PET Scan (Ga-68 DOTATATE) – Becoming More Prevalent with Higher Sensitivity
  • If Noninvasive Imaging Fails: Invasive Imaging
    • Endoscopic Ultrasound (EUS) – Generally Preferred Next Step 24
    • Selective Arterial Secretin Stimulation with Hepatic Venous Sampling 25
    • Selective Visceral Angiography
  • Consider Surgical Exploration with Palpation or Intraoperative Ultrasound if High Suspicion but All Imaging Negative

PNET on Imaging: (A) CT, (B) EUS, (C) SRS, (D) Functional PET 26

Treatment

Surgical Resection (Treatment of Choice)

  • < 2-3 cm: Enucleation
    • Additional Requirements:
      • Single Lesion
      • ≥ 2-3 mm From the Main Pancreatic Duct (Reduce Leak Risk)
      • Well-Encapsulated
      • No Local Invasion
    • The Preferred Approach if Able
  • > 2-3 cm: Surgical Resection
    • Head/Neck: Pancreaticoduodenectomy
    • Body/Tail: Distal Pancreatectomy (Concurrent Splenectomy if Malignancy is Suspected)
    • Entire Pancreas: Total Pancreatectomy

Medical Management for Gastric Acid Hypersecretion

  • Measures:
    • High-Dose Proton Pump Inhibitor (PPI) – First Line 14,27,28
    • Somatostatin Analogs (SSAs) if PPIs Fail 29,30
      • Octreotide or Lanreotide
  • Used Preoperatively or for Patients that are Not Surgical Candidates or in Unresectable Metastatic Disease

Liver-Directed Therapy

  • Resection of Metastases if Able
  • Radiofrequency Ablation (RFA) or Cryoablation 31,32
  • Hepatic Artery Embolization 33

Additional Options in Surgically Unresectable Disease

  • Chemotherapy 34,35
  • Radiation Therapy 36,37
    • Pancreatic Neuroendocrine Carcinomas Were Previously Considered to be Resistant to Radiation

References

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