SABCS 2020 featured several interesting presentations in the field of radiotherapy. The PRIME 2 study investigated the impact of omitting postoperative whole breast radiotherapy in older, low-risk women with early invasive breast cancer. Outcomes of the phase III BIG 3-07/TROG 07.01 trial were also reported providing improved insights into the optimal radiation dose and fractionation schedule for non-low risk ductal carcinoma in situ of the breast. Other interesting topics included the comparison of patient and physician reports of toxicity after breast radiotherapy and the finding that radiation therapy improves survival in early-stage HER2-positive breast cancer with a high-levels of tumour infiltrating lymphocytes. Finally, we report on the results of a retrospective analysis assessing the feasibility of radiation therapy de-escalation in patients with stage I, node-negative, HER2-positive breast cancer.