Having previously demonstrated that ER inhibition is an effective radiosensitisation strategy in ER+, AR-low breast cancers [22] and AR inhibition is a potentially effective radiosensitisation strategy in AR+/ER− breast cancer [8], the purpose of this study was to assess the effectiveness of AR inhibition as a radiosensitisation strategy in AR+/ER+ breast cancer models. Here, ESR1 is linked to breast cancer.