KRAS and colorectal carcinoma: Studies have shown that ctDNA positivity increases with CRC stage, through measuring proportions of cases that are ctDNA positive with methylated BCAT1/IKZF1 (Pedersen et al., 2015; Symonds et al., 2018), KRAS mutations (Shin et al., 2017), and with a panel of mutations (KRAS, BRAF, EGFR, PIK3CA) (Kidess et al., 2015).