ESR1 and breast cancer: Although, in the study conducted by Margolis et al., Ktrans showed higher values in Ki67+ tumours, resulting in more aggressive behaviours, the study reported by Carmona-Bozo et al. on 29 ER+ breast cancer patients showed a negative correlation between hypoxic fraction and Ktrans (r = −0.33) and νe (r = −0.38), suggesting lower levels of hypoxia with an increase in Ktrans and νe.