ESR1 and breast carcinoma: In women that are ≥70 years old with clinical stage I (T1N0) estrogen-receptor positive (ER+) breast cancer on endocrine therapy, the Cancer and Leukemia Group B (CALGB) 9343 clinical trial data initially published in 2004 increasingly supports that lumpectomy alone compared to lumpectomy and breast radiotherapy results in equivalent survival and acceptable cancer control (5, 6).