Pathologic complete response to neoadjuvant imatinib of a gastric stromal tumor with concomitant mutations in KIT: A case report and literature review

Abstract

The gastrointestinal stromal tumors "GISTs" are driven in 90% of cases by somatic mutations in the proto-oncogene receptor tyrosine kinase KIT also known as (C-KIT, CD117) or the platelet-derived growth factor receptor alpha PDGFRA also known as (CD140A, PDGFR2). These two genes are located in the same chromosomal region 4q2, and code for the same sub-family of proteins within the family of receptor tyrosine kinases. 1 Most primary KIT mutations in GISTs occur in exon 11 or exon 9, and rarely in the exons 13, 14, or 17. However, PDGFRA mutations are most often in exon 18 (mainly the p.D842V substitution) and rarely exon 12. KIT and PDGFR inhibition is the primary therapeutic modality for unresectable and metastatic GISTs. 2 Imatinib mesylate competes with ATP for the ATP-binding site of several receptor tyrosine kinases. It selectively blocks the activation of KIT and PDGFR