To our knowledge, only one study has directly addressed circulating 27-HC, 25-HC, and breast cancer survival in a small patient cohort (n = 58) [14], while several other studies indirectly assessed the association between 27-HC and prognosis by evaluating the levels of protein or mRNA expression of the enzymes converting cholesterol to 27-HC (CYP27A1) or metabolizing 27-HC to downstream metabolites (CYP7B1) [8, 9, 11–13]. Here, CYP7B1 is linked to breast cancer.