The link to tumor burden is supported by studies that demonstrate significant correlations of ctDNA levels with tumor volume including r = 0.50 for ctDNA mutations (Tie et al., 2015), r = 0.74 for methylated SEPT9 (Bhangu et al., 2018), and r = 0.75 for methylated vimentin (Overman et al., 2016); as well as studies that found that ctDNA (panel of 14 mutated genes) was strongly associated with maximum tumor diameter (p = 0.00002) and sum of tumor diameter (p = 0.00009) (Osumi et al., 2019). Here, SEPTIN9 is linked to neoplasm.