Breast cancer experts from the Memorial Sloan Kettering Cancer Center in New York suggested the omission of radiotherapy in the case of ductal carcinoma in situ, in patients aged 70 and older, and in the case of invasive estrogen-receptor positive disease smaller than 3 cm in size without nodal involvement and with negative resection margins. The gene discussed is ESR1; the disease is ductal breast carcinoma in situ.