The PRADAIIBE study is a multicentric phase 3 clinical trial, investigating the effects of radiotherapy timing on breast reconstruction results, in breast cancer patients. This study will be recruiting Belgian breast cancer patients. They can participate if there is an indication for both surgical removal of the complete breast tissue, in the form of a skin or nipple sparing mastectomy (SSM/NSM) and postoperative radiotherapy treatment, as well as a wish for breast reconstruction. During the screening visit the eligibility criteria are checked, demographic information is collected, a baseline assessment is performed and the participant will be randomly assigned to either the control or intervention group. Those assigned to the control group will follow the standard of care treatment in the classic sequence of oncological surgery followed by radiotherapy. The breast reconstruction surgery will take place either at the same time (mostly tissue expander implantation) as the oncological surgery, or at a delayed moment. Patients assigned to the intervention group will receive the same standard of care treatments, with the difference that the radiotherapy is administered before the oncological surgery (preoperative radiotherapy). In this arm of the study, the breast reconstruction is performed at the same time as the oncological surgery (Immediate Breast Reconstruction). After the treatment is finished the patients will return for follow up visits at 3 months, 1 year, 2 years, 5 years and 10 years after finishing the study treatments. An additional visit is provided at 3 months after the last session of radiotherapy for patients undergoing delayed reconstruction. During these baseline and follow-up visits, 2 questionnaires (BREAST-Q v2; EQ5D5L) will be completed, photographs of the breasts will be taken, adverse events will be recorded and oncological recurrence will be evaluated. The key result (primary outcome) is breast satisfaction (BREAST-Q v2, BQ-score) at 1 year follow-up. Secondary outcomes are defined as BREAST-Q-scores, EQ5D5L-scores, photograph evaluations (AIS-TAS), adverse events, treatment pathway duration, and pathological complete response rates. These are assessed per follow-up visit. The tertiary outcome follows oncological recurrence. With the results from this study the goal is to improve patient satisfaction, QoL and aesthetic results of breast reconstruction after breast cancer treatment, as well as reduce postoperative complications and treatment duration.