While robust expression data for breast cancer in primary tumors and subsequent metastases are not available, a study using multiple MAGE-recognizing primers (MMRPs) that can simultaneously detect 6 MAGE-A gene subtypes (MAGE-A1-MAGE-A6) expressed by circulating tumor cells in patients with breast cancer suggests that increasing MAGE-A gene expression predicts for tumor progression or recurrence [44]. Here, MAGEA6 is linked to breast cancer.