Utility of KRAS mutation detection using circulating cell‐free DNA from patients with colorectal cancer

Abstract

In this study, we evaluated the clinical utility of detecting KRAS mutations in circulating cell‐free (ccf)DNA of metastatic colorectal cancer patients. We prospectively recruited 94 metastatic colorectal cancer patients. Circulating cell‐free DNA was extracted from plasma samples and analyzed for the presence of seven KRAS point mutations. Using the Invader Plus assay with peptide nucleic acid clamping method and digital PCR,KRAS mutations were detected in the ccfDNA in 35 of 39 patients previously determined to have primary tumors containing KRAS mutations using the Luminex method, and in 5 of 55 patients with tumors containing wild‐type KRAS. Curative resection was undertaken in 7 of 34 patients with primary and ccfDNA KRAS mutations, resulting in the disappearance of the mutation from the cell‐free DNA in five of seven patients. Three of these patients had tumor recurrence and KRAS mutations in their ccfDNA reappeared. Epidermal growth factor receptor blockade was administered to 24 of the KRAS tumor wild‐type patients. Of the 24 patients with wild‐type KRAS in their primary tumors, three patients had KRAS mutations in their ccfDNA and did not respond to treatment with epidermal growth factor receptor (EGFR) blockade. We also detected a new KRAS mutation in five patients during chemotherapy with EGFR blockade, before disease progression was detectable with imaging. The detection of KRAS mutations in ccfDNA is an attractive approach for predicting both treatment response and acquired resistance to EGFR blockade, and for detecting disease recurrence.

Clinical relevance of circulating tumor DNA assessed through deep sequencing in patients with metastatic colorectal cancer

“…We observed significant association of ctDNA level with liver metastasis and sum of the tumor diameter in metastatic sites, which were commonly reported to be strongly associated with ctDNA level. 20,34,35 While the controversial or null association of ctDNA level with the lung, lymph node and peritoneal metastasis, tumor markers, primary tumor location, and number of metastatic organs has been reported, 20,34,36,37 we observed significant association between ctDNA level and lymph node metastasis, number of metastatic organs, and tumor markers (CEA, CA19-9, and LDH). Although different sample size and sampling bias may cause these discordant results, the above associations should be further validated by using a larger number of samples.…”

Liquid biopsy - emergence of a new era in personalized cancer care

“…Therascreen ARMS assay (Qiagen), Competitive Allele-Specific TaqMan PCR (castPCR, Life Technologies), and Invader Plus assay with peptide nucleic acid clamping (InvClamp assay (Hologic, Inc. Marlborough, MA, USA) are widely used in both clinical and trial settings to determine equivalence for KRAS mutation. castPCR plate includes primer and probes for additional KRAS mutations and BRAF V600E, which are not included in Therascreen or Invader Plus [66]. There is US FDA approval of the Therascreen KRAS RGQ PCR Kit (Qiagen) and the Cobas® KRAS Mutation Test (Roche Molecular Systems, Inc.) for detecting druggable mutations in formalin-fixed paraffin-embedded (FFPE) tissues of specific cancers.…”

Liquid Biopsy for the Management of Patients with Colorectal Cancer

“…We previously reported the detection of KRAS mutations in cfDNA from 5 of 55 mCRC patients (9%) with wild-type KRAS in their primary tumors [23]. Other researchers reported that KRAS mutation in cfDNA is a negative biomarker of EGFR blockade chemotherapy [23][24][25][26][27].…”