Serial Monitoring of Circulating Tumor DNA in Patients With Metastatic Colorectal Cancer to Predict the Therapeutic Response

Abstract

Early biomarkers of therapeutic responses can help optimize the treatment of metastatic colorectal cancers (mCRC). In this prospective exploratory study, we examined serial changes of plasma-circulating tumor DNA (ctDNA) in 41 mCRC patients receiving first-line chemotherapies and tested its association with treatment outcomes according to radiological assessments. Using next-generation sequencing technologies, we profiled somatic mutations in 50 cancer-related genes in ctDNA before each of the first four treatment cycles. We observed mutations in 95.7% of pre-treatment ctDNA samples. Using mutations of the maximal frequency in each pre-treatment plasma ctDNA sample as the candidate targets, we computed log2 fold changes of ctDNA levels between adjacent treatment cycles. We found that ctDNA reductions as early as prior to cycle 2 predicted responses after cycle 4. Log2 fold changes of ctDNA after cycle 1 (ctDNA log2 (C1/C0)) > −0.126 predicted progressive disease, with an accuracy of 94.6%. These patients also showed significantly worse progression-free survival than those with ctDNA log2 (C1/C0) ≤ −0.126 (median 2.0 vs. 9.0 months; P = 0.007). Together, the present exploratory study suggests that early changes in ctDNA levels detected via targeted sequencing are potential biomarkers of future treatment responses in mCRCs.

Patient specific circulating tumor DNA fingerprints to monitor treatment response across multiple tumors

“…These properties make ctDNA a promising tool to monitor tumor progression and treatment response [ 4 – 6 ]. Several studies have demonstrated that ctDNA had higher sensitivity and specificity than the traditional methods such as radiological imaging and blood protein biomarkers under some conditions [ 7 , 8 ]. In metastatic colorectal cancer (CRC), the different patterns of ctDNA level change correlated with tumor responses in patients [ 9 , 10 ].…”

Clinical Application of Next-Generation Sequencing as A Liquid Biopsy Technique in Advanced Colorectal Cancer: A Trick or A Treat?

“…Some of the CRC-specific studies also defined some treatment-related entry criteria, such as treatment with anti-VEGF or anti-EGFR agents, at the first [48,52,53] or later lines of therapy [44]. Others required patients receiving surgical treatment for liver metastases [54] or who were chemotherapy-naïve [45,55,56,57].…”

“…Some studies only aimed at assessing the feasibility and clinical relevance of NGS plasma assays [49,50,62,63,66,67], while several others employed NGS in serial samples to monitor response to treatment [45,46,56,57,60,68] and/or to study the development of resistance to administered therapies [44,48,51,52]. The goal of two studies was to decipher the genomic landscape of cfDNA to grasp CRC heterogeneity [59,64].…”

“…The same panel was possibly used in a third study, which refers to analysis of “hotspot and targeted regions of 22 genes”, “with an NGS-based panel that has been approved for in vitro clinical diagnostics in colon and lung cancer patients”, also on an Ion PGM [50]. On the same instrument, the Ion AmpliSeq Cancer Hotspot Panel v2 (50 genes) was used in one study [59] and the SV-CA50-ctDNA panel (50 genes) was used in another [56]. The AVENIO ctDNA Expanded Kit (77 genes), NCC Oncopanel (90 genes), and the oligo-gene SOMATIC 1 MASTRTM v2 were each used once, with NextSeq 500, HiSeq 2500, and MiSeq sequencers, respectively [44,52,58].…”

“…When it comes to library preparation protocols, also summarized in Table 2, most of the studies reported the use of the AmpliSeq Library Kit, either v.2 [54,56,59] or Plus [51], and Oncomine assays, either Solid Tumor DNA [50,61] or Colon cfDNA [62], all of which are amplicon-based enrichment approaches, as is the CRC01 kit reported by another group [66]. Several studies performed hybrid capture-based enrichment, with SureSelect [57] and Guardant assays [49,63,64,65,67].…”