Progression-free survival (PFS) was referred to be decreased in breast cancer [71], RCC [60,61], ESCC [62], head and neck cancer [46], T-cell NHL [64] and gastric cancer [67] patients expressing high MCT1 levels; in all of these studies (with the exception of the studies by Zhao et al. [64] and Johnson et al. [71]) MCT1 remained as an independent predictor of cancer progression. This evidence concerns the gene SLC16A1 and breast cancer.