ESR1 and breast cancer: Further analyses of 10 year breast cancer specific mortality were carried out within subgroups of patients (Table 3), specified by age, menopausal status, ethnic group (Maori, Pacific Island, NZ European), stage (1+2, 3+4), systemic treatment (chemotherapy and hormonal therapy, chemotherapy alone), mode of detection (screening, symptomatic), receptor status (ER and PR positive, ER and PR negative, mixed), type of surgery (breast conservation, mastectomy, no surgery), and post-operative radiotherapy (yes, no).