Intraoperative radiotherapy with electrons (ELIOT) for early breast cancer: the European Institute of Oncology experience

Partial breast irradiation (PBI) as an alternative to whole breast irradiation (WBI) is an attractive approach tested in several phase II and a few phase III studies, using different modalities of irradiation. Intraoperative radiotherapy (RT) with electrons allows the reduction of a whole course of WBI to a single session during surgery. The European Institute of Oncology (Milan, Italy) conducted a series of investigations aimed proving the safety and the effectiveness of intraoperative RT as a full dose PBI. The single dose of 21 Gy was calculated to be theoretically equivalent to a full course of conventional WBI. This ultimate form of hypofractionation carried some concern regarding the long-term impact on breast parenchyma. Phase I and II studies and a number of off-protocol patients have shown feasibility and good short-term results in both disease control and cosmesis. The results of the ELIOT randomized phase III trial comparing intraoperative RT to conventional WBI are discussed in the context of a worldwide scenario including other four randomized studies and one metanalysis, so far. From the analysis of the available data, the adequate patient selection emerges as mandatory to make intraoperative RT and other PBI modalities a reasonable alternative to conventional WBI. Further investigations are required to fully understand the weight of clinical and histologic variables classically associated with increased risk of local recurrence. In addition, the role of molecular classification in the pattern of recurrence after PBI will be more and more predominant.