Intraoperative electron radiotherapy (IORT)

This technique uses a mobile linear accelerator that produces a variable energy electron beam which is applied directly in the operating room. After complete excision of the tumour confirmed by extemporaneous histology, the surgeon inserts a lead and aluminium plate on the pectoralis major chest muscle in order to protect the underlying structures and organs (chest wall, heart and lung).

The residual mammary gland is then temporarily reconstructed above the plate. In accordance with the thickness of the remaining gland, the dose of energy to be administered is determined by the radiation oncologist, depending upon whether it is an exclusive IORT treatment or a boost that will be completed by external irradiation of the entire mammary gland. The electrons are applied directly to the surgical site and the mammary gland is reconstructed using a variable diameter cylindrical applicator. After treatment, the protective plate is removed and the operation is completed in the usual manner.

The Milan studies were the first to analyse the results of intra-operative radiotherapy. They cover more than 8000 patients with a unifocal primary breast carcinoma, who were selected in accordance with strict criteria. The various reports published by the European Institute of Oncology show the same rate of recurrence after 10 years of monitoring of either intraoperative radiation therapy or external radiation therapy. Currently, IORT is reserved for post-menopausal patients who have a unifocal tumour with well-defined biological characteristics and a diameter of less than 2.5 cm, but without lymph node involvement. These indications will probably be expanded in coming years, and this will allow more women to benefit from this technique.

For some patients, who do not meet all the requirements for an exclusive IORT, we propose a «boost» IORT. In these cases, radiation therapy is administered in two steps: firstly during surgery (partial IORT) and secondly about 3 weeks after the operation. In this case, the supplementary external radiotherapy is shorter as it is administered in 13 fractions over a period of 2.5 weeks.