Over the past 30 years, there has been a dramatic change in the local management of breast cancer, with radical operations being replaced by more conservative surgical procedures, together with the widespread use of radiotherapy. This shift has been prompted by results from randomised clinical trials that have clearly demonstrated breast-conserving surgery followed by radiotherapy is equivalent to more radical procedures in terms of local control and overall survival . However, although the surgery is now conservative, the radiotherapy remains radical and may be overtreatment. Evidence for this comes from large studies of breast-conserving therapy where more than 90% of early breast recurrences were found to occur at the site of the original primary tumour site, whether or not radiotherapy was given and/or the margins were involved [2, 3]. The development of a novel radiotherapy device enabled the launch of an international randomised controlled trial designed to compare intraoperative versus conventional external beam radiotherapy in women with early breast cancer .