Treatment of refractory gastrointestinal stromal tumor using pazopanib

Gastrointestinal stromal tumor (GIST) is the most common sarcoma in the gastrointestinal tract. Its incidence rate is 1–1.5 per 100,000 per year (1), consistent to the worldwide incidence of approximately 10–20 million people per year (2). Although GIST is generally resistant to both radiation therapy and chemotherapy, over the last two decades GIST has become one of the most controllable sarcoma by molecularly targeted therapies (3). Most GIST express aberrantly activated transmembrane tyrosine kinase (TK) receptors, either KIT or PDGRFA (4). KIT mutation accounts for 80% of GISTs and is most common in exon 11 (65%) followed by exon 9 (8%) (1,2). PDGFRA mutation accounts for less than 10% of cases. GIST without identifiable KIT or PDGFRA mutations are collectively called wild-type and account for 10–15% of patients (5).