An increasing proportion of breast cancer patients treated by mastectomy wish for a breast reconstruction. If post-mastectomy radiation therapy is recommended, the reconstruction is often delayed until 6 - 12 months after completion of chemotherapy and radiation therapy due to risk of complication that might delay adjuvant treatment. At this time the native skin over the removed breast cannot be used in the reconstruction, resulting in a suboptimal aesthetic outcome. In the delayed-immediate reconstruction method, a skin sparing mastectomy and reconstruction with implant is performed at primary surgery, to save the native skin under radiation therapy, thereby improving the chance for a good aesthetic outcome at the final delayed reconstruction. In this trial breast cancer patients treated by mastectomy and loco-regional radiation therapy is randomized to either delayed reconstruction or delayed-immediate reconstruction. The complication rate as well as morbidity, aesthetic outcome and psychological well-being after delayed-immediate reconstruction will be compared with delayed reconstruction