MRI-guided Single Dose Preoperative Radiotherapy in Low-risk Breast Cancer

In this multi-center single arm interventional cohort study 70 patients will be treated with single dose preoperative partial breast irradiation (PBI). Breast conserving surgery will be performed 12 months following PBI to assess pathologic response. Response monitoring following PBI includes MRI (3T and 7T), liquid biopsies and biopsy of the irradiated tumor. Results from this trial can change the current treatment of patients with early stage breast cancer. The single dose PBI can be of benefit for all patients who are suitable for postoperative PBI according to current guidelines. If pathologic complete response can be accurately predicted by (one of) the abovementioned response monitoring modalities, the need for surgery will become disputable. Moreover, in patients without expected pathologic complete response, the burden of radiotherapy can be minimized from 3-4.5 weeks of radiotherapy to a single dose of radiotherapy.