**6.2 Detecting aberrant DNA methylation**

Several studies have explored the use of DNA methylation markers that may have a role in CRC screening and diagnosis, and which in some cases may have similar sensitivity and specificity to the aforementioned *Septin 9* methylation assay (for example, *APC*, *MGMT*, *RASSF2A*, *Wif-1*, *ALX4*, *NEUROG1*) [94–99]. More compelling is the evidence suggesting that the use of a combination of DNA methylation markers—a multigene methylation signature—may enhance sensitivity and specificity compared with single biomarker detection [94, 96]. Such an assay, utilising the methylation of both *BCAT1* and *IKZF1*, has shown promising results in this setting as previously discussed [51, 52, 64, 100].

## **6.3 Using CTC, extracellular vesicles, and microRNA as adjuncts biomarkers**

This chapter has highlighted the recognisable potential for a paradigm shift with the use of ctDNA for the molecular diagnosis and monitoring of CRC, as well as its multiple drawbacks when used in isolation. Notably, ctDNA is largely unable to evaluate biomarkers other than genomic aberrations. An alternative approach is the use of tools such as CTC, extracellular vesicles, and circulating microRNAs (miRNA), in conjunction to ctDNA, to overcome these limitations.
