It was examined in BC patients that both total cfDNA level and CTC count were correlated with OS [17], that cfDNA integrity was correlated with CTC presence [20], that SOX17 promotor methylation and ESR1 methylation were highly concordant in ctDNA and CTCs [19,23], and that cfDNA and CTCs showed overlapping mutation profiles [17]. This evidence concerns the gene SOX17 and breast cancer.