Gastrinoma

Incidence and Presentation

• Second most common functioning PNET
• Mean age 50
• 75% sporadic, 25% associated with MEN1
• Gastrin production is independent from the usual amino acid and peptide stimulation
  • Also not suppressed by high pH
  • Can be stimulated (instead of inhibited) by secretin
• 90% located in the gastrinoma triangle

  • 60% located in duodenum (most in D1)

Zollinger-Ellison Syndrome

• Acid hypersecretion
  • Abdominal pain
  • And resultant secretory diarrhoea
  • Peptic ulcer diseas
  • Gastroesophageal reflux disease

Diagnosis

• Should consider in all with
  • Intractable peptic ulcers (esp. jejunal ulcers!)
  • Severe oesophagitis
  • Persistent secretory diarrhoea
  • Measure serum gastrin levels
    • NB: Pernicious anaemia and PPI use may increase gastrin level too
      • But lack gastric acid hypersecretion
      • Need to stop PPI 2/52 prior to doing gastrin levels
• Elevated serum gastrin with a pH < 2 in gastric aspirate is diagnostic of ZES
  • If pH > 3 without PPIs, is not ZES
• If diagnosis in question, can do secretin stimulation test

Localisation

• Same as general PNET localisation principles
• Use water PO contrast to see duodenal lesions better
• SRS Indicated if not localised on CT/MRI
  • Almost all Gastrinomas express somatostatin receptors
• If not located pre-op
  • Explore entire abdomen, in particular cul-de-sacs
  • Carefully inspect gastrinoma triangle
  • Use IO USS as adjunct
  • Consider duodenotomy for mucosal palpation

Treatment

• Prevent acid secretion and relieve symptoms
  • PPIs - often higher doses needed
• Operative treatment
  • When curative disease possible
  • Palliative cytoreduction for symptom control
• Enucleate if small, well encapsulated
  • Large unencapsulated lesions should have segmental resection (Whipple’s or distal pancreatectomy)
    • Whipple’s may increase disease free survival in MEN 1
      • Recurrent tumours most often found in Duodenum

• 50% present with metastatic disease

  • Focus on symptom control (high dose PPIs)
  • Total Gastrectomy no longer indicated unless
    • Can’t tolerate PPIs
    • Concerns with gastric carcinoid tumour related to prolonged hypergastrinaemia
    • Gastrectomy cures all symptoms but does not affect disease progression

Prognosis

• 50% of patients completely resected will have symptomatic or biochemical recurrence at 5yrs
• Patients can live > 20yrs with residual disease
  • Aggressive surgery indicated
• 10yr survival
  • Aggressive form – 30%
  • Non-aggressive form – 90%
• Best predictor of survival is the presence of liver mets
• LN mets are not predictive