Over a median of 12.2 years follow-up in cohort 1, high CYP27A1 expression was associated with impaired survival, specifically after 5 years from diagnosis among all patients [overall survival (OS), HRadjusted = 1.93, 95%CI = 1.26–2.97, P = 0.003; breast cancer-specific survival (BCSS), HRadjusted = 2.33, 95%CI = 1.28–4.23, P = 0.006] and among patients ≥ 55 years presenting with ER+ tumors [OS, HRadjusted = 1.99, 95%CI = 1.24–3.21, P = 0.004; BCSS, HRadjusted = 2.78, 95%CI = 1.41–5.51, P = 0.003]. The gene discussed is ESR1; the disease is breast cancer.