ESTRO 2025 - Abstract Book

S4399

RTT - Treatment planning, OAR and target definitions

ESTRO 2025

software to create 3D surface scans of each participant’s torso. These were converted to Dicom and imported into Raystation 2023b (Raysearch). CTVs were estimated using the external breast contour and sternal notch as references. Two-field plans were created to determine whether suitable beam access/CTV coverage could be achieved, without: (i) beams clipping the contralateral breast or arms, and (ii) beams entering through the patient positioner. Results: Figure 1 summarises the number of participants for whom suitable plans were achieved, for each position. For one participant achieving a suitable arms-up plan wasn’ t possible but the arms-back position was feasible. Using the bra reduced: (i) the superior-inferior length of the treatment fields (Figure 2) and (ii) inframammary skin fold (ISF) measurements. Overall, ISF measurements were greater for arms-back positions relative to arms-up positions. Optimal beam angles were found to vary with superior-inferior position within the breast, suggesting that >2 chair angles would prove beneficial.

Figure 1: Beam access

Figure 2: Field lengths in different positions

Conclusion: Surface scans indicate that arms-up positioning in this Bra should provide suitable beam access for upright photon treatments of the breast, i.e. enabling CTV coverage, without beams clipping the contralateral breast/arms, or entering through the backrest. For patients who struggle raising their arms, arms-back upright positioning may be suitable. In conclusion, upright positioning appears promising for photon beam access for RT of the breast. Further research is required to consider internal anatomy.

Keywords: Upright, Breast, New techniques