Table 1b describes disease characteristics and treatment. At diagnosis, 6236 (81.1%) had invasive cancers, 4714 (61.3%) had no nodal involvement; 4957 (64.5%), 4368 (56.8%) and 1490 (19.4%) had ER-, PR- and HER2-positive tumours respectively. Other sociodemographic, medical history, breast cancer risk factors, disease and treatment characteristics that were explored can be found in Supplementary Table S1. Here, ESR1 is linked to breast cancer.