**7. Conclusion**

The data generated from basic research, retrospective clinical studies, and limited prospective studies all support the potential role of ctDNA as a biomarker for early disease, minimal residual disease, recurrence, response to therapy, and emerging drug resistance mechanisms in the management of CRC. Nevertheless, multiple challenges need to be overcome before this promising technology can be adopted into routine clinical practice.

Firstly, a crucial question is whether the genomic aberrations detected in ctDNA actually drive tumour progression. It is also still unknown whether ctDNA will ever be able to mirror the heterogeneity or molecular subclones of CRC in a given


#### **Table 2.**

*Currently recruiting and upcoming clinical trials assessing ctDNA in CRC (http://clinicaltrials.gov).*

**69**

*Current Utility and Future Applications of ctDNA in Colorectal Cancer*

patient. Further clarity is also needed regarding intra-patient variability in ctDNA levels, the dynamics of ctDNA release and ctDNA clearance. Such knowledge will inform the design of future studies, particularly regarding the optimal timing of

Secondly, to determine the true value of ctDNA analysis in guiding decision-making, carefully designed and well-controlled prospective trials are needed to address clinically relevant questions for various settings. An important question, for example, is how to utilise ctDNA detection as a biomarker of minimal residual disease after resection of a stage I–III CRC. Can we use this biomarker to make decisions about the necessity, type and duration of adjuvant therapy and guide follow-up or surveillance scheduling? Another question is how to use ctDNA to monitor for the emergence of molecular resistance and can we use this approach to inform us about timely adaptation of further treatment lines? **Table 2** lists selected currently recruiting and upcom-

ctDNA assessment relevant to the appropriate therapeutic intervention.

ing clinical trials assessing the utility of ctDNA in various settings in CRC.

Importantly, pre-analytical considerations, ctDNA detection techniques, and interpretation of results need to be standardised. On review of the current literature, it will be obvious to the reader that there is a high level of heterogeneity amongst various techniques. Consequently, results that are obtained from one study cannot be interpreted in the same way and applied to other techniques. Standardisation will ensure that there is consensus regarding the sensitivity and specificity of utilised techniques and that there are established cut-off levels, for each clinical setting. Finally, it is important to acknowledge that the use of promising novel technologies will have cost implications which may hinder their rapid

The relative frequency of a gene variant in a specimen, expressed as a percentage or fraction

Sampling and analysis of tumour-based material (e.g. CTC, ctDNA, RNA, exosomes) from

describing a range of high throughput methods capable of the simultaneous analysis of

The pre-analysis phase in the laboratory testing process and may include sample collection, handling, processing, transport and storage. These factors can affect the subsequent

The ability of an intervention or test to demonstrate benefit in patient care compared to not

CfDNA Cell-free DNA. DNA fragments found circulating in body fluids, including plasma or serum. CfDNA may come from a variety of sources including tumour cells

NGS Next generation sequencing (NGS) or massively parallel sequencing are broad terms

PCR Polymerase chain reaction. A laboratory technique used to make many copies (amplification) of a specific DNA sequence of interest

CtDNA Circulating-tumour DNA. A proportion of cfDNA that is tumour-derived

body fluids such as blood, urine and pleural fluid

thousands to millions of DNA molecules

analysis outcomes

using the intervention or test

*DOI: http://dx.doi.org/10.5772/intechopen.82316*

entry into routine clinical practice.

**Glossary**

Allele frequency

Liquid biopsy

Preanalytical

Clinical utility

## *Current Utility and Future Applications of ctDNA in Colorectal Cancer DOI: http://dx.doi.org/10.5772/intechopen.82316*

patient. Further clarity is also needed regarding intra-patient variability in ctDNA levels, the dynamics of ctDNA release and ctDNA clearance. Such knowledge will inform the design of future studies, particularly regarding the optimal timing of ctDNA assessment relevant to the appropriate therapeutic intervention.

Secondly, to determine the true value of ctDNA analysis in guiding decision-making, carefully designed and well-controlled prospective trials are needed to address clinically relevant questions for various settings. An important question, for example, is how to utilise ctDNA detection as a biomarker of minimal residual disease after resection of a stage I–III CRC. Can we use this biomarker to make decisions about the necessity, type and duration of adjuvant therapy and guide follow-up or surveillance scheduling? Another question is how to use ctDNA to monitor for the emergence of molecular resistance and can we use this approach to inform us about timely adaptation of further treatment lines? **Table 2** lists selected currently recruiting and upcoming clinical trials assessing the utility of ctDNA in various settings in CRC.

Importantly, pre-analytical considerations, ctDNA detection techniques, and interpretation of results need to be standardised. On review of the current literature, it will be obvious to the reader that there is a high level of heterogeneity amongst various techniques. Consequently, results that are obtained from one study cannot be interpreted in the same way and applied to other techniques. Standardisation will ensure that there is consensus regarding the sensitivity and specificity of utilised techniques and that there are established cut-off levels, for each clinical setting. Finally, it is important to acknowledge that the use of promising novel technologies will have cost implications which may hinder their rapid entry into routine clinical practice.

