Compared to the prevalence of alterations found in samples from patients with de novo metastatic disease (3.9% [CI: 2.4–5.5] for ESR1 and 29.7% [CI: 26.1–33.2] for TP53), tumors from patients relapsing within 1 year on adjuvant ET were characterized by substantially higher prevalence of TP53 alterations, whereas tumors from other recurrent patients (>1 years on adjuvant ET) had higher ESR1 alteration prevalence (19.1% [CI: 15.3–22.8]). The gene discussed is ESR1; the disease is metastatic neoplasm.