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

Abstract

Because circulating tumor DNA (ctDNA) studies focusing on only one or a few genes to monitor the disease progress or treatment response are unlikely to find its clinical significance, the development of cell‐free DNA (cfDNA) panel covering hundreds of mutation hot spots is important for the establishment of clinically practical ctDNA detection system. We enrolled 101 patients with metastatic colorectal cancer (mCRC) who received chemotherapy. Amplicon‐based genomic profiling of 14 genes, which are commonly mutated in CRC, in plasma by next‐generation sequencing (NGS) was carried out to evaluate the feasibility of this assay and was compared with their clinical parameters and RAS status in matched tissue samples. Somatic mutations of the 14 genes in plasma cfDNA were detected in 88 patients (87.1%) with mCRC. Mutations in TP53, KRAS, and APC genes were detected in 70 (69.3%), 39 (38.6%), and 24 (23.7%) patients, respectively. Mutant allele frequencies in plasma were significantly associated with metastasis (liver, P = 0.00004, lymph node, P = 0.008, number of metastatic organs, P = 0.0006), tumor markers (CEA, P = 0.000007, CA19‐9, P = 0.006, LDH, P = 0.00001), and tumor diameter (maximum, P = 0.00002, sum of diameter, P = 0.00009). The overall concordance rate of RAS status between ctDNA and matched tissue was 77.2% (78/101). Our data confirmed that mutant allele in cfDNA can be sensitively detected by amplicon‐based NGS system. These results suggest that ctDNA could be a novel diagnostic biomarker to monitor changes in mutational status and tumor burden in patients with mCRC.

Clinical utility of circulating tumor DNA for colorectal cancer

“…Patients with liver metastasis showed significantly higher ctDNA compared to patients without metastasis at this site . In contrast, peritoneal metastasis was not correlated with ctDNA . The relationship between ctDNA and number of metastatic organs is controversial .…”

“…In contrast, peritoneal metastasis was not correlated with ctDNA . The relationship between ctDNA and number of metastatic organs is controversial . These data suggest that intrinsic biological characteristics of tumors may impact ctDNA release as well as tumor burden.…”

“…To better understand the biology of ctDNA, it is important to consider the relationship between clinicopathological factors and ctDNA. Associations between clinicopathological factors and ctDNA are shown in Table . ctDNA is strongly correlated with initial tumor burden as estimated from the RECIST criteria, suggesting that tumor volume is significantly related to the detection of ctDNA in plasma.…”

“…Associations between clinicopathological factors and ctDNA are shown in Table . ctDNA is strongly correlated with initial tumor burden as estimated from the RECIST criteria, suggesting that tumor volume is significantly related to the detection of ctDNA in plasma. Patients with liver metastasis showed significantly higher ctDNA compared to patients without metastasis at this site .…”

Comparison of Somatic Mutation Profiles Between Formalin-Fixed Paraffin Embedded Tissues and Plasma Cell-Free DNA from Ovarian Cancer Patients Before and After Surgery

“…While its levels correlate with disease grading, staging, and metastasis, this can vary among patients. 9,[21][22][23][24][25][26] In addition to ctDNAs, circulating nucleic RNAs and miRNAs, circulating tumor cells, and extracellular vesicles represent a new approach called ''Liquid biopsy'' that allow to analyze the genetic and epigenetic profiles from many body fluids, especially blood serum and plasma, saliva, urine, and so on. 26,27 Liquid biopsy can provide benefits when standard tissue biopsy cannot be performed due to difficulty in accessing tissue specimens, and it is equally beneficial in monitoring tumor heterogeneity, the emergence of drug resistance, and the determination of minimal residual disease following surgery and therapy.…”