Breast-conserving therapy (BCT), consisting of local excision of the tumor followed by whole breast radiotherapy, is nowadays considered standard of care for early stage breast cancer. For patients at low risk of local recurrence, partial breast irradiation (PBI) is an alternative treatment. The rationale for PBI is that irradiation of only the tumour bed and surrounding area will result in less toxicity, while maintaining an acceptable low local recurrence rate as most of the local recurrences occur at or near the original tumor site. Because the target volume is smaller than with WBI, reduced toxicity is expected and a higher dose per fraction can be applied. As a result, overall treatment time can be reduced. There are various methods to deliver PBI, including brachytherapy, intraoperative radiation therapy, and external beam radiation therapy (EBRT). Multiple studies showed less toxicity and similar or improved cosmetic outcome after PBI using EBRT.