CST6 and breast cancer: In early breast cancer we found no association between the EpCAM-positive CTC-fraction and 42 available paired primary tumours in respect to the promoter methylation status of any of the three genes studied (Table 3); concordance for SOX17 promoter methylation was observed only in 15/42 (35.7%) cases, while the concordances were very low for CST6, and BRMS1. In the metastatic setting, there was a concordance for 21/33 (63.6%) of cases for SOX17 promoter methylation, while there was no concordance for CST6 and BRMS1.