Circulating Tumor DNA Is Capable of Monitoring the Therapeutic Response and Resistance in Advanced Colorectal Cancer Patients Undergoing Combined Target and Chemotherapy

Abstract

Colorectal cancer (CRC) is a highly lethal disease worldwide. The majority of patients receiving targeted therapy or chemotherapy develop drug resistance, while its molecular mechanism remains to be elucidated. The plasma circulating tumor DNA (ctDNA) exhibited the potential in identifying gene variations and monitoring drug resistance in CRC treatment. In this study, we monitored the ctDNA mutational changes in advanced CRC patients underwent first-line therapy with bevacizumab and cetuximab combined with chemotherapy. The mutation spectrum of 43 patients was established by a 605gene next-generation sequencing (NGS) panel. The baseline measurement shows that genes with the highest mutation frequency were TP53 (74%), APC (58%), KRAS (40%), SYNE1 (33%), LRP1B (23%), TOP1 (23%), and PIK3CA (21%). Mutations in TP53, APC, and KRAS were detected in 29 paired plasma and tissue samples with the consistency of 81, 67, and 42%, respectively. Clinically targetable gene mutations, such as APC, RNF43, SMAD4, BRAD1, KRAS, RAF1, and TP53, were also identified in ctDNA. The overall consistency between ctDNA and tissue samples was 54.6%. Alleviation of mutational burden in BRAF, KRAS, AMER1, and other major driving genes was observed following the first-line therapy. Patients with KRAS and TP53 mutations in tissues appeared to benefit more than the wild-type counterpart. The dynamic change of plasma mutation status was consistent with the tissue tumor burden and was closely correlated with disease progression. In conclusion, ctDNA monitoring is a useful method for molecular genotyping of colorectal cancer patients. Dynamic changes in resistance can be sensitively monitored by gene variation status, which potentially helps to develop treatment strategy.

Detection of KRAS mutations in liquid biopsies from metastatic colorectal cancer patients using droplet digital PCR, Idylla, and next generation sequencing

“…A study by Cao et al used a 605-gene panel to study mutations in both plasma ctDNA and CRC tissues at baseline and after first-line treatment (chemotherapy plus bevacizumab and/or cetuximab). This study discovered new mutations in ATM and NF1 after treatment and a new mutation in PDGFRB during disease progression [21]. A study by Yamauchi et al analyzed plasma samples and pre-treatment tumor samples from 21 mCRC patients undergoing treatment with bevacizumab and oxaliplatin-or irinotecan-based chemotherapy.…”

The diagnostic accuracy of digital PCR, ARMS and NGS for detecting KRAS mutation in cell-free DNA of patients with colorectal cancer: A systematic review and meta-analysis

“…In the study by Kidess-Sigal et al [ 50 ], the authors compared KRAS , BRAF , and PIK3CA status between circulating tumor cells, ctDNA, and tissue samples of 15 mCRC patients using a 4-gene NGS panel, and in the 3 patients with both ctDNA and primary tumor samples available, the calculated concordance rate for KRAS was 66.7% (2/3), with 1 false-positive case. In the study by Cao et al [ 34 ], a 605-gene NGS panel was used to analyze tumor and plasma samples of CRC patients, and from 35 patients with KRAS status available in both tumor and plasma, the calculated sensitivity was 75.0% and specificity was 82.6%. Using a customized targeted NGS library kit (SureSelect QXT, Agilent Technologies, USA), Yao et al [ 38 ] investigated KRAS/NRAF/BRAF mutations in plasma and tumor samples of mCRC patients, and concordance rate of KRAS was 81.25% in 64 patients, with sensitivity of 66.7% and specificity of 90.0%.…”

“…Several studies involved in this systemic review and meta-analysis attempted to investigate possible roles of liquid biopsy in early detection or monitoring of the disease (e.g. driver mutations, resistance to targeted therapeutics), and therefore included CRC patients of different stages (I-IV) [ 14 , 18 , 19 , 29 , 34 , 36 , 39 ]. Since both primary and metastatic CRC patients were involved in those studies [ 14 , 18 , 19 , 39 ], we extracted their data separately.…”

“…Since both primary and metastatic CRC patients were involved in those studies [ 14 , 18 , 19 , 39 ], we extracted their data separately. Three studies were excluded from the subgroup analysis because we cannot separate their data by groups of primary and metastatic CRC [ 29 , 34 , 36 ]. As shown in Table 3 , compared to primary CRC, mCRC showed higher pooled sensitivity [0.79 (95%CI: 0.76–0.82)] and specificity [0.88 (95%CI: 0.86–0.90)].…”

Signed in Blood: Circulating Tumor DNA in Cancer Diagnosis, Treatment and Screening

“…Importantly, responses were observed in five of nine patients who received EGFR inhibitors, including patients who showed ctDNA EGFR amplifications, but no amplifications in the tissue DNA [64]. Taken together, it is apparent that ctDNA molecular alterations play a vital 79 Burden/Aggressiveness of Disease Resistant ctDNA alterations that may emerge months before changes in scans are noted and can inform an understanding of mechanisms of resistance in colorectal, lung, and breast cancers, as examples [80][81][82]. For instance, ctDNA was used to identify early resistance mutations in patients with HER2-amplified breast cancer; PI3K/mTOR pathway alterations were the major cause of resistance [83].…”