Inclusion Criteria:  Histopathologically confirmed breast cancer operated by breast conserving surgery with clear margins Indication to adjuvant radiotherapy including boost radiotherapy Clearly identified primary tumor region preferably by radiopaque clips Primary wound healing after breast conserving therapy without signs of infection Pre- and/or postoperative chemotherapy and endocrine therapy were permitted when indicated Written informed consent  Exclusion Criteria:  Patients operated by mastectomy No indication for boost radiation Resection margins positive for disease or insufficient identification of the boost volume Indication for radiotherapy of the regional lymph nodes History of prior breast or thoracic radiotherapy Extended postoperative seroma at the beginning of radiotherapy Psychiatric disorders or psychological disabilities thought to adversely affect treatment compliance Pregnant or lactating patients and woman of child bearing potential, who lacked effective contraception