ESR1 and cancer: Undertreatment consisted of omission of radiation therapy in 59 of the 125 patients treated with breast conservation, omission of axillary node surgery in 301 of the 377 elderly patients with invasive cancers, omission of chemotherapy in 66 of 102 elderly patients with involved nodes, and omission of hormonal therapy in 85 of 386 elderly patients with estrogen receptor positive cancers.