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General information

Over the past few decades, the major change in the surgical management of early breast cancer has been the shift towards minimally invasive approaches. These include breast conservation surgery (BCS) and sentinel lymph node (SLN) biopsy. BCS was introduced to reduce the physical and psychological consequences of removing the whole breast.

Postoperative radiotherapy to the whole breast with boost to the tumour bed is regarded as an essential adjunct to BCS and cannot be safely omitted. There is overwhelming evidence that this approach decreases the risk of local recurrence and improves survival (Fisher et al. 1991 ). The aim of radiotherapy is to selectively kill any residual tumour cells without damaging normal cells. This is achieved by generating free radicals, which cause single- or double-stranded breaks in the cell’s DNA. Considering that tumour cells have less ability to repair DNA damage than normal cells and are more frequently in the radiosensitive part of the cell cycle, they are most vulnerable to the effects of radiation therapy.

The results of many clinical trials and observational studies have demonstrated that around 90 % of local recurrences after BCS occur within the same quadrant of the breast that harboured the primary tumour (index quadrant). This observation raises the question of whether whole breast radiotherapy is necessary and whether radiotherapy to the index quadrant of the breast alone would be sufficient for the management of breast cancer patients. This has led to growing interest in accelerated partial breast irradiation (APBI), which aims to decrease the volume of breast treated and increase the daily fraction size of radiation.

INTRABEAM is a mobile, miniature X-ray generator powered by a 12-V supply. Accelerated electrons strike a gold target at the tip of a 10-cmlong drift tube with a diameter of 3 mm, resulting in the emission of low-energy X-rays (50 kV) in an isotropic dose distribution around the tip. The irradiated tissue is kept at a fixed, known distance from the source by spherical applicators to ensure a more uniform dose distribution. The tip of the electron drift tube sits precisely at the epicentre of a spherical plastic applicator, the size of which is chosen to fit the cavity after the breast cancer has been excised. Using this method, the walls of the tumour cavity are irradiated to a biologically effective dose (20 Gy to the tissue in contact with the applicator) that rapidly attenuates over a distance of a few centimetres. As a result, surrounding healthy tissue is spared and the device can be used in an unmodified operating theatre.