Elkin et al. demonstrated a reduction in all-cause mortality by approximately 16% among older patients with estrogen receptor-negative BC who received systemic chemotherapy;47 however, older patients may have an increased risk of cardiac toxicity, treatment-induced myelodysplasia, or acute leukemia.48,49 Consequently, the indications for chemotherapy in patients aged ≥90 years remain very rare. Here, ESR1 is linked to acute leukemia.