ESR1 and breast cancer: McCormick et al. reported that 88% of women aged 70 years and older with stage I, estrogen receptor-positive breast cancer received radiotherapy after breast-conserving surgery, even after the National Comprehensive Cancer Network (NCCN) guidelines for elderly breast cancer patients stated the omission of radiotherapy after breast-conserving surgery in women meeting the CALGB 9343 entry criteria who were prescribed hormonal agents in 2009 [15].