Gastrointestinal stromal tumors (GISTs) result from mutations of a growth factor receptor gene, C-KIT. Some are caused by previous radiation therapy to the abdomen for other tumors.
Tumors are slow growing, and malignant potential varies from minimal to significant. Most (60 to 70%) occur in the stomach, 20 to 25% in the small bowel, and a small number in the esophagus, colon, and rectum. Average age at presentation is 50 to 60.
Symptoms of GISTs vary with location but include bleeding, dyspepsia, and obstruction.
Diagnosis of GISTs is usually by endoscopy, with biopsy and endoscopic ultrasonography for staging.
Treatment of GISTs is surgical removal. The tyrosine kinase inhibitor imatinib can be used when tumors are positive for the KIT protein CD117; it is effective for patients with unresectable and/or metastatic malignant GISTs and also as adjuvant treatment following resection in adults (1). For imatinib-refractory tumors, sunitinib and regorafenib can be used.
Avapritinib, another tyrosine kinase inhibitor, should be used as first-line therapy for patients with a platelet-derived growth factor receptor alpha (PDGFRA) exon 18 mutation, including PDGFRA D842V mutations.
1. Dematteo RP, Ballman KV, Antonescu CR, et al: Adjuvant imatinib mesylate after resection of localised, primary gastrointestinal stromal tumour: A randomised, double-blind, placebo-controlled trial. Lancet 373(9669):1097–1104, 2009. doi: 10.1016/S0140-6736(09)60500-6. Clarification and additional information. Lancet 374(9688):450, 2009.