Considering the low frequency of methylated samples in our study, the sensitivity of RARB (20.69%), GSTP1 (10.34%), and RARB + GSTP1 (31.03%) shows the difficulties of the Methylight assay to correctly classify breast cancer patients parting from free circulating bisulfite‐converted DNA, a situation that could be improved using higher initial plasma volume (>1.5 mL) or a more sensitive technique like digital PCR (Cui et al., 2018). Here, RARB is linked to breast cancer.