In summary, breast conserving therapy (BCT) is an effective, save and widely used treatment technique for early breast cancer. Radiotherapy has shown to give better local control and survival benefit and is an integrated part of BCT. The simultaneous integrated boost (SIB) technique is a new treatment technique in breast irradiation. In this technique the whole breast is irradiated simultaneous with boosting the tumour bed, as part of BCT. Late radiation-induced toxicity has not been investigated in patients treated with radiotherapy using this technique. Proposed study will study the late radiation-induced toxicity, describe patients-rated complaints, quality of life, survival and local control curves in patients treated for early breast cancer with breast-conserving surgery in combination with radiotherapy with the SIB technique as compared to sequential radiotherapy treatment.