ESR1 and breast cancer: Combining fulvestrant (an Estrogen Receptor (ER) degrader) with the PI3K-AKT signalling inhibitors alpelisib (PI3Kαi) or capivasertib (AKTi) provides benefit in ER+ breast cancer (BC) patients with PIK3CA altered and PIK3CA, PTEN and AKT-1 altered tumours respectively7,8.