Breast conserving therapy (BCT) including postoperative irradiation of the remaining breast tissue is generally accepted as the treatment of choice for the vast majority of patients with early stage breast cancer, resulting in advantages of improved cosmesis and quality of life (QOL) as compared to mastectomy (MX). The question whether post operative irradiation is mandatory in all patients and, herewith, over-treating almost a half of them, remains one of the most controversial issues in BCT. To properly answer this question, a randomised prospective multi-centre study was launched in January 2001, based on long-term follow-up data of the Milan III trial comparing BCT with or without postoperative irradiation. The main aim was to assess the cumulative incidence of local recurrence after conservative surgery with (CS+RT) vs. without breast irradiation (CS) . Added values of the study were to avoid the inconvenience and the risk of side-effects of radiation therapy and to prevent unnecessary mastectomies in hospitals where the facilities for radiation treatment are not available. From January 2001 until December 2005, 749 patients from 11 centres in Italy were randomly assigned to CS+RT (radiotherapy: homogenous breast irradiation 50 Guy +10 Guy boost) or to CS. Main patients and tumours characteristics were fairly well balanced between treatment groups. The evaluation after a median follow-up of 60 months is now in.