Gastrointestinal stromal tumors (GISTs)

Question 1

Most common location

Answer 1

stomach and proximal small intestine (but can occur anywhere throughout the GI tract)

Question 2

tissue of origin

Answer 2

stromal (connective tissue)

Question 3

Most common mutation in intestinal GIST

Answer 3

c-KIT exon 9

Question 4

Lymph node involvement common with GIST?

Answer 4

nodal involvement is rare in GIST

Question 5

How typically diagnossed

Answer 5

• Some incidentally discovered during endoscopy or CT

- some due to nonspecific symptoms

Question 6

Clinical presentation

Answer 6

• occult GI bleed (28%)
• Asymptomatic 13-18%
• abdominal pain
• usually early satiety + bloating
• unless ulcerate

Question 7

GIST metastatic pattern

Answer 7

liver and peritoneum (rare nodal mets)

Question 8

Biopsy required?

Answer 8

• preoperative bx not generally recommended if patient is operable and imaging is consistent

Question 9

Clinical behavior of GISTs

Answer 9

Highly variable (some indolent, others aggressive)

Question 10

Management of localized GIST

Answer 10

All greater than 2cm = surgery w/ adjuvant imatinib based on risk stratification (significantly reduces risk of recurrence)

Question 11

Clinical course

Answer 11

• Indolent but frequently recur

Question 12

Management of metastatic GIST’s

Answer 12

Imatinib

Question 13

General response to imatinib in metastatic disease

Answer 13

Most of the time growth is controlled, but complete responses are only rarely achieved and most acquire resistance so median to progression is 2 years

Question 14

Adjuvant for GIST

Answer 14

Imatinib depending on RFs

Question 15

most common mutation associated with gastric GIST

Answer 15

c-KIT exon 11

Question 16

Gene mutation associated with best prognosis in GIST

Answer 16

c-KIT exon 11 duplication

Question 17

adjuvant therapy for GIST? Indication + duration

Answer 17

Determine recurrence risk with MSKCC nomogram
IF c-KIT mutant AND high risk → imatinib 400 mg daily for 3 years