Some of the approved included; Cancer antigen 15-3 (CA 15-3) and Cancer antigen 27.29 (CA 27.29) kits that measure Mucin 1 (MUC1) levels in peripheral blood, assessment of carcino-embryonic antigen (CEA) levels in blood and ER, PgR, HER2 status of the primary tumour. Here, ESR1 is linked to cancer.