OBJECTIVE: Imatinib is a standard treatment for metastatic gastrointestinal stromal tumor (GIST). Imatinib resistance is mostly caused by secondary mutations in C-KIT. The antitumor effect of second-line agents is correlated with the type of secondary mutation: indeed, sunitinib is effective against tumors with C-KIT exon 13 or 14 mutations. We investigated whether secondary C-KIT mutations can be detected in circulating tumor DNA (ctDNA) from peripheral blood. METHODS: This study included 4 patients who underwent resection of imatinib-resistant GIST. Tumor-specific mutations in each tumor were determined by Sanger sequencing. ctDNA was extracted from peripheral blood obtained before and after the treatment of imatinib-resistant lesions. Each of the secondary target mutations in ctDNA was investigated, using a next-generation sequencer. RESULTS: Imatinib-resistant lesions had single-nucleotide substitutions in C-KIT exon 13 in 3 patients and exon 18 in 1 patient. Identical secondary C-KIT mutations could be detected in ctDNA with a mutant fraction range of 0.010-9.385%. One patient had growth of an imatinib-resistant tumor containing a C-KIT exon 13 mutation, and the fraction of ctDNA decreased after initiation of sunitinib. CONCLUSION: Detection of secondary C-KIT mutations in ctDNA could be useful for the selection of targeted agents and prediction of antitumor effects.
OBJECTIVE:Imatinib is a standard treatment for metastatic gastrointestinal stromal tumor (GIST). Imatinib resistance is mostly caused by secondary mutations in C-KIT. The antitumor effect of second-line agents is correlated with the type of secondary mutation: indeed, sunitinib is effective against tumors with C-KIT exon 13 or 14 mutations. We investigated whether secondary C-KIT mutations can be detected in circulating tumor DNA (ctDNA) from peripheral blood. METHODS: This study included 4 patients who underwent resection of imatinib-resistant GIST. Tumor-specific mutations in each tumor were determined by Sanger sequencing. ctDNA was extracted from peripheral blood obtained before and after the treatment of imatinib-resistant lesions. Each of the secondary target mutations in ctDNA was investigated, using a next-generation sequencer. RESULTS:Imatinib-resistant lesions had single-nucleotide substitutions in C-KIT exon 13 in 3 patients and exon 18 in 1 patient. Identical secondary C-KIT mutations could be detected in ctDNA with a mutant fraction range of 0.010-9.385%. One patient had growth of an imatinib-resistant tumor containing a C-KIT exon 13 mutation, and the fraction of ctDNA decreased after initiation of sunitinib. CONCLUSION: Detection of secondary C-KIT mutations in ctDNA could be useful for the selection of targeted agents and prediction of antitumor effects.
Authors: Pieter A Boonstra; Jourik A Gietema; Albert J H Suurmeijer; Matthew R Groves; Fernando de Assis Batista; Ed Schuuring; Anna K L Reyners Journal: Oncotarget Date: 2017-11-26
Authors: Pieter A Boonstra; Arja Ter Elst; Marco Tibbesma; Lisette J Bosman; Ron Mathijssen; Florence Atrafi; Frits van Coevorden; Neeltje Steeghs; Sheima Farag; Hans Gelderblom; Winette T A van der Graaf; Ingrid M E Desar; Jacqueline Maier; Jelle Overbosch; Albert J H Suurmeijer; Jourik Gietema; Ed Schuuring; Anna K L Reyners Journal: Oncotarget Date: 2018-02-14