Intraoperative radiotherapy in early stage breast cancer: potential indications and evidence to date

Following early results of recent studies of intraoperative radiotherapy (IORT) in the adjuvant treatment of patients with early breast cancer, the clinical utility of IORT is a subject of much recent debate within the breast oncology community. This review describes the intraoperative techniques available, the potential indications and the evidence to date pertaining to local control and toxicity. We also discuss any implications for current practice and future research.Adjuvant radiotherapy (RT) following surgery in the treatment of early stage breast cancer delivered with external beam RT (EBRT) permits breast conservation with low rates of in-breast tumour recurrence (IBTR).¹ When IBTR occurs, however, the recurrence is most commonly located in the same quadrant as the index tumour.² Furthermore, pathological examination of mastectomy specimens demonstrates that malignant and/or pre-malignant cells are rarely found >4 cm from the index lesion.³ Such data have given rise to the hypothesis that irradiating only the part of the breast tissue in proximity to the index tumour will be associated with local control rates comparable with those seen after adjuvant whole-breast EBRT. Such partial breast irradiation would also be expected to be associated with less toxicity given the reduced volume of non-target tissue irradiation.Partial breast RT may be delivered by a number of techniques, including EBRT, interstitial brachytherapy and intraoperative RT (IORT).^4,5 The use of IORT has been reported in a range of tumour sites, including the breast, head and neck, lung, limbs (sarcoma), gastrointestinal and genitourinary tracts, and lung.^6–12 For most tumour sites, the premise of IORT is to deliver RT directly and therefore potentially more accurately to the tumour itself or to the tumour bed whilst delivering minimal dose to the surrounding normal tissues. Although not in routine clinical practice, in previous studies of IORT, the IORT has been delivered in combination with EBRT as a “boost” or as the sole RT modality.^6,13In the context of adjuvant treatment for early breast cancer, IORT has most commonly been delivered to the tumour bed after surgical excision of the tumour, and a number of technical approaches have been described. IORT to the breast has been used both to deliver a tumour-bed boost in conjunction with EBRT and as definitive adjuvant RT treatment instead of whole-breast EBRT.^13,14 Until recently, there has been a lack of randomized Phase III trial evidence comparing IORT with EBRT in either setting. This review describes the different IORT techniques available, the potential clinical utility of IORT, the evidence to date and the implications for standard practice and future research.