Most women who undergo partial mastectomy (lumpectomy) surgery for breast cancer also complete a course of radiotherapy delivered to the whole of the affected breast (called external beam radiotherapy, EBRT). EBRT has been shown to reduce the risk of cancer recurring in the breast, but it can cause unpleasant side-effects, and requires women to attend radiotherapy centres for 20 days after surgery, which can cause serious difficulties for women who live far from radiotherapy centres, especially those in remote or very rural areas. In some cases, women who are eligible for lumpectomy may end up undergoing full mastectomy, simply because they cannot meet the demands of subsequent radiotherapy treatment required by partial tissue removal.