None of the potential advantages have been clearly demonstrated in a controlled fashion although there are sound theoretical reasons that a boost will improve local control. Holland's landmark paper using radiologic-pathologic correlation of mastectomy specimens, whilst finding residual foci beyond the boundaries of cosmetically acceptable resection margins, also found most of the residual tumour relatively close to the index mass. There is a known dose-response for control of breast cancer. Kurtz reported a doubling of the longterm recurrence rate when the dose to the tumour bed was less than 75 Gy or delivered at less than 8 Gy per week from 15% to 30% using telecesium following lumpectomy. Treating the entire breast to doses above 50 to 54 Gy in 5 weeks is associated with significantly worse cosmesis, hence the common use of a boost. There are as yet no controlled comparisons published however Beadle reported a 50% increase in the rates of poor cosmesis when a boost was employed. Borger has demonstrated that the risk of fibrosis increases fourfold with every 100 cm3 increase in boost volume. Accurate localisation of the tumour bed for boost delivery is difficult in the absence of radioopaque clips (uncommonly employed by our referral base). The use of electrons to deliver the boost has been reported to decrease the cosmetic outcome compared to I192 because of telangiectasia, although this is controversial with other reports indicating superior results with electrons, which is the modality available at St George and Wollongong. The latter avoids hospitalisation. There is at least one other randomised multicentre study being conducted testing the value of a boost by the EORTC in Europe but no results are yet available.