Institut Curie guidelines on breast target volume delineation for patients treated in lateral position

To develop guidelines for and describe the delineation of breast for patients treated in lateral position and to transform this three-dimensional technique based on the virtual simulation to volume-based modern intensity-modulated irradiation technique.

In our department, during the daily delineation, radiation oncologists specialized in breast cancer treatment sought consensus on the delineation of clinical treatment volume of the breast through dialogue based on cases. A radiation oncologist delineated clinical treatment volumes on CT scans of five to 20 patients, followed by a discussion and adaptation of the delineation between all radiation oncologists of the team. The consensus established between clinicians was discussed, corrected and improved. All patients were delineated in treatment position; skin markers were used to visualize the breast tissue after careful palpation.

Breast clinical treatment volume was situated and delineated between pectoral muscle and 5mm below the skin (dosimetric considerations), within the space outlined by skin markers, that showed the limits of the palpable breast tissue. In lateral position some vessels were very useful to define the limits as rami mammarii (from thoracica interna) for the internal one and thoracica lateralis for the external. This is the first atlas proposed for the delineation of the breast clinical treatment volumes for breast cancer using alternative technique of breast irradiation (lateral).

This atlas will be helpful for the volume definition in our daily practice of breast irradiation in lateral position and can open perspectives to develop also atlases for other alternative techniques as treatment in prone position.