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Management of GIST. Dr Kwan Ming Wa Tuen Mun Hospital. Contents. Mainly concern about Oncogensis Surgical treatment Targeted therapy. Introduction. GIST the most common Sarcoma of the GI tract derived from the Interstitial cells of Cajal. Oncogenesis of GIST.
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Management of GIST Dr Kwan Ming Wa Tuen Mun Hospital
Contents • Mainly concern about • Oncogensis • Surgical treatment • Targeted therapy
Introduction • GIST • the most common Sarcoma of the GI tract • derived from the Interstitial cells of Cajal
Oncogenesis of GIST Mutated KIT receptor become autonomous and cell proliferation become uncontrolled KIT Receptor Gene expression Signal-Transduction ATP ADP Signal Molecule Plasma Membrane Earl W. Sutherland (Nobel Prize – 1971)
Understanding of the oncogenesis is the key to the advances of diagnosis and targeted therapy
Targeted therapy (Glivec) Competitive inhibition of Tyrosine Kinase Autonomous KIT Receptor ATP ADP Gene expression Plasma Membrane
Clinical features of GIST • Incidence • Worldwide 10-20/ million • Tuen Mun ~13 cases/ year • Median age at 60 • Sex ratio 1:1
Presentation • GI Bleeding • the most common presenting symptom • Mass effect • when tumour is large enough • Small GIST • Usually found incidentally
Preoperative biopsyNot advocated • GIST is highly vascular and friable • Risk of bleeding • Risk tumour rupture • Risk tumour dissemination and early recurrence
Imaging for diagnosis and staging • CT scan, endoscopy and EUS are commonly used to diagnose GIST • A well circumscribed, vascular mass associated with stomach/ intestine • Staging primary GIST • CT scan and CXR is sufficient • metastasis is usually confined to peritoneum and the liver • For complicated disease, PET-CT • Recurrent disease/ extraperitoneal metastasis
Surgery • The primary treatment for resectable GIST • The goal is complete resection of the mass without disruption of the pseudocapsule
GIST generally displace rather than infiltrating the surrounding structure • Achieving negative margin is usually possible
Dissection of lymph node does notprolong survival or delay recurrence • Connolly EM, Br J Surg 2003 • Sammiian L, Am Surg 2004
Outcome after complete resection • 5yr survival (overall) : 48-65% • Poor outcome is associated with • Big tumour size (>5cm) • High mitotic figure (>5/50HPF)
Conventional adjuvant therapy • Chemotherapy: refractory • Radiotherapy: limited use
Targeted therapy • Evidence of benefit in • Treatment of advanced GIST • As adjuvant to primary tumour resection
10 years or until death Placebo x 1 year F O L L O W Primary GIST (≥ 3 cm) Glivec 400mg (or 800mg) x 2 years Complete Gross Resection Recurrence Glivec 400mg x 1 year ACOSOG Z9001: A randomized, double blind study of adjuvant Glivec versus placebo following resection of primary GIST Design:
ACOSOG Trial Prematurely Stopped Due to Superior Rates of Recurrence Free Survival (RFS) with Glivec • Data monitoring committee evaluated data on >600 pts with complete resection of primary GIST • At 1 year follow-up, 97% of patients on Glivec arm were free of recurrence compared with 83% of patients on placebo arm • Approximately 65% less likely to experience recurrence within two years • All patients will be unblinded, and patients in the placebo arm will be offered 1 year of Glivec Available at: http://www.cancer.gov/newscenter/pressreleases/GISTtrial
Treatment model Normal Pre-Cancer Cancer Metastatic Cancer prevention Treatment Stage Primary +/- Adjuvant systemic therapy 1st Line 2rd Line