ESR1 and breast cancer: First, the long-term follow-up data from the CALGB 9343 trial further confirmed that addition of adjuvant radiation (to endocrine therapy) for women age 70 years or older with ER + early-stage breast cancer does not translate to an advantage in overall survival, distant disease-free survival, or breast preservation.27 Whelan et al.28 pushed this envelope further, including tumor biology.