Gastro Medicine - Gastrointestinal stromal tumour

Question 1

What is the epidemiology of Gastrointestinal stromal tumour?

Answer 1

• GIST’s are not common tumours (10 per million) and originate primarily from the interstitial pacemaker cells (of Cajal).
• Up to 70% occur in the stomach, the remainder occurring in the small intestine (20%) and the colon and rectum (5%). Up to 95% are solitary lesions and most are sporadic.
• The vast majority express CD117 which is a transmembrane tyrosine kinase receptor and in these there is a mutation of the c-KIT gene.

Question 2

What is the goal of surgery?

Answer 2

• The goal of surgery is resection of the tumour with a 1-2cm margin of normal tissue.
• As a result extensive resections are not required.
• Unfortunately there is a high local recurrence rate, the risk of which is related to site, incomplete resections and high mitotic count.
• Salvage surgery for recurrent disease is associated with a median survival of 15 months.

Question 3

What is the prognosis in patients?

Answer 3

• The prognosis in high risk patients is greatly improved through the use of imatinib, which in the ACOSOG trial (imatinib vs placebo) improved relapse rates from 17% to 2%.
• In the UK it is advocated by NICE for use in patients with metastatic disease or locally unresectable disease.