Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the GI tract, primarily found in the stomach and small bowel, with management revolutionized by imatinib. Surgical treatment is focused on achieving complete resection with negative margins, utilizing techniques such as laparoscopic approaches, while neo-adjuvant and adjuvant therapies are applied based on tumor characteristics and risk. Prognostic factors and mutation analysis guide treatment decisions, particularly in cases of metastatic GIST or locally advanced tumors.

1. Gastric GISTs
Dr. Harsh Shah
MS, DNB(GI), MCh (GI)
GI & HPB Surgeon
Kaizen Hospital
Ahmedabad

2. Gastrointestinal Stromal Tumours
• Most common mesenchymal tumour of GI Tract
• Interstitial cells of Cajal
• Wide spectrum of clinical activity
• Low risk
• High risk
• Imatinib (Gleevec) revolutionized the management

3. GIST Location
• Esophagus(<1%)
• Stomach(60%)
• Duodenum(5%)
• Small bowel(30%)
• Colon-rectum(4%)
Demitri et al, 2010, JNCCN

4. Diagnosis
• CT scan/MRI
• UGIE/Biopsy
• Diagnosis doubtful -
Lymphoma
• Neo-adjuvant therapy
planned
• IHC Markers
• cd-117
• DOG-1
• CD-34
• SDHB

5. Principles of Surgical Treatment
• R0 resection
• Histologically negative margins - adequate
• Lymphadenectomy not required except for
• Pathologically enlarged nodes
• SDHB Deficient GIST
Aim:
• Organ preservation
• Prevention of tumour rupture

6. Surgical Techniques
• Open
• Minimally invasive
• Laparoscopic wedge
resection
• Laparoscopic intragastric
surgery (LIGS)
• Laparoscopic &
endoscopic co-operative
surgery (LECS)

7. Laparoscopic wedge resection of GIST
• Favorable lesion
• Exophytic
• Anterior wall
• Greater curvature
• Localization – Dye, Lap ultrasound
• Minimal handling
• Prevent tumour rupture
• Preserve tumour pseudocapsule
• Removal in specimen bag
• Spillage
• Port site seeding

9. Laparoscopic Intragastric surgery(LIGS)
Ohashi et al 1995
• <5 cm
• Posterior wall or upper half of stomach
• Laparoscope or endoscope guidance
• Cuffed ports
• Specimen removal (Orally/Trans
abdominally)
• Trauma to gastric wall

10. LIGS

11. LECS
(Laparoscopic & Endoscopic Cooperative surgery)
Hiki et al, Surg Endosc 2008
• Upto 5 cm, without mucosal ulceration
• Located near EGJ & Pylorus
• Causes minimal gastric transformation
• Spillage of gastric contents & tumour cells

12. LECS

13. Locally Advanced GIST
Definition
• Margin negative resection not possible
• Major organ resection required
• Multi-organ resection
Plan of treatment
• Neo-adjuvant therapy  Surgery  Adjuvant therapy
• Bleeding, Obstructing, Perforation – Emergency surgery

14. Neo-adjuvant Therapy
• Atleast 6-12 months
• Imatinib (400mg/day) to be stopped immediately prior to surgery
• Sunitinib (50mg/day, 4+2) to be stopped 1 week in advance
• Regorafenib (160mg/day, 3+1) as a third line

15. Mutation analysis & Targeted therapy
• Kit exon 11 Sensitive to low dose Imatinib
• kit exon 9  Imatinib 800mg
• Kit Exon 13,17
• PDGFRA D842V
• WT(SDHB)
• WT GIST (SDHB)  Sunitinib
Not sensitive to Imatinib

16. Prognostic Factors

17. Response Evaluation
Response evaluation
• PET – reduced activity at 2 weeks
• Contrast CT/MRI – reduced density,
enhancement at 8 weeks
‘Nodule within Nodule’ appearance
of Imatinib Resistance

19. Locally advanced GIST

20. Adjuvant therapy
• Intermediate & high risk GIST (Easily resectable GIST)
• >10% risk of recurrence
• All cases of locally advanced GIST
• 3 years Imatinib Joensuu et al, JAMA, 2010

21. Metastatic GIST
• Imatinib (6-12 months)
• Surgery to be offered
• Responsive
• Limited progression
• Macroscopically complete
resection

22. ‘GIST’ of today’s talk
• Mutation analysis – for drug selection
• Surgery is mainstay for easily resectable >2cm lesions
• Neoadjuvant therapy(6-12 months) surgery for locally advanced
tumours
• Adjuvant therapy for 3 years all GIST with >10% risk of metastasis
• Imatinib for metastatic disease