Background: EGFR activating mutations predict sensitivity to tyrosine kinase inhibitors (TKIs) in NSCLC. Although initial responses are commonly observed, patients inevitably progress as a consequence of acquired resistance. Secondary mutations in the EGFR domains (Gainor JF, Shaw AT. J Clin Oncol 2013;31:3987) or in cross-talking pathways (i.e., KRAS, Martin P, et al. J Thorac Oncol 2013;8:530) have been detected in biopsies of resistant cancers. However, the location of the tumor and the risk of complications are serious limitations to re-biopsies in NSCLC. Alternatively, detection of somatic mutations in circulating cell-free DNA (ccfDNA) in plasma could be instrumental to a better understanding of the dynamics of the genetic shift of tumors under stress conditions caused by drug treatments. Methods: Twenty-eight NSCLC patients displayed an activating EGFR mutation or ALK translocation in the primary tumor and received a TKI against EGFR (gefitinib or erlotinib, n= 25) or ALK (crizotinib, n= 3). Blood (5 ml) was collected after tumor progression and DNA was extracted from plasma using QIAamp circulating nucleic acid kit and tested for EGFR and KRAS mutations using Rotor-Gene Q PCR (Qiagen, Valencia, CA) or digital droplet PCR (Bio-Rad, Hercules, CA). Results: EGFR mutations of the primary tumor were confirmed in ccfDNA of 35.7% patients after progression under TKIs (L858R 7.1%, exon 19 insertions/deletions 28.6%). The EGFR T790M mutation was in 10.7% of patients’ ccfDNA. Interestingly, 10 (35.7%) patients displayed a codon 12 KRAS mutation in ccfDNA, including all patients with ALK+ tumors, after TKI treatment. The KRAS mutations were not detectable in their primary tumor using conventional diagnostic approaches. Pre-treatment plasma samples were available in only two patients and KRAS mutations were not detected. Conclusions: The observation of KRAS mutations in plasma of patients with tumors carrying EGFR mutations or ALK rearrangements after TKI treatment suggests an important role of this oncogene in acquired resistance.
Association of KRAS mutations in cell-free circulating tumor DNA with occurrence of resistance to TKIs in NSCLC
DEL RE, MARZIA;PETRINI, IACOPO;Citi, V;MINUTI, GABRIELE;FALCONE, ALFREDO;DANESI, ROMANO
2014-01-01
Abstract
Background: EGFR activating mutations predict sensitivity to tyrosine kinase inhibitors (TKIs) in NSCLC. Although initial responses are commonly observed, patients inevitably progress as a consequence of acquired resistance. Secondary mutations in the EGFR domains (Gainor JF, Shaw AT. J Clin Oncol 2013;31:3987) or in cross-talking pathways (i.e., KRAS, Martin P, et al. J Thorac Oncol 2013;8:530) have been detected in biopsies of resistant cancers. However, the location of the tumor and the risk of complications are serious limitations to re-biopsies in NSCLC. Alternatively, detection of somatic mutations in circulating cell-free DNA (ccfDNA) in plasma could be instrumental to a better understanding of the dynamics of the genetic shift of tumors under stress conditions caused by drug treatments. Methods: Twenty-eight NSCLC patients displayed an activating EGFR mutation or ALK translocation in the primary tumor and received a TKI against EGFR (gefitinib or erlotinib, n= 25) or ALK (crizotinib, n= 3). Blood (5 ml) was collected after tumor progression and DNA was extracted from plasma using QIAamp circulating nucleic acid kit and tested for EGFR and KRAS mutations using Rotor-Gene Q PCR (Qiagen, Valencia, CA) or digital droplet PCR (Bio-Rad, Hercules, CA). Results: EGFR mutations of the primary tumor were confirmed in ccfDNA of 35.7% patients after progression under TKIs (L858R 7.1%, exon 19 insertions/deletions 28.6%). The EGFR T790M mutation was in 10.7% of patients’ ccfDNA. Interestingly, 10 (35.7%) patients displayed a codon 12 KRAS mutation in ccfDNA, including all patients with ALK+ tumors, after TKI treatment. The KRAS mutations were not detectable in their primary tumor using conventional diagnostic approaches. Pre-treatment plasma samples were available in only two patients and KRAS mutations were not detected. Conclusions: The observation of KRAS mutations in plasma of patients with tumors carrying EGFR mutations or ALK rearrangements after TKI treatment suggests an important role of this oncogene in acquired resistance.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
