ESTRO 2025 - Abstract Book

S4326

RTT - Treatment planning, OAR and target definitions

ESTRO 2025

delineated by a radiation oncologist, according to our clinical routine. PTVs for the breast, RLN and IMN were created by adding an isotropic margin of 5 mm. The PTV and the CTV for the breast were cropped by 5 mm from the skin. TP was performed independently by 7 treatment planners with different levels of experience. The field setup for the 3D-CRT technique was used according to our clinical guidelines (Figure 1). The prescribed dose was 40.05 Gy (2.67 Gy x 15 fractions). TP was performed in Monaco (Elekta, Stockholm, Sweden), using the Collapsed Cone algorithm with a dose grid of 3 mm for the dose calculation. Plan evaluation was made in terms of target dose coverage and dose-volume (DV) metrics to the OARs according to the Swedish national guidelines for breast cancer RT. The results were also compared to the actual clinical treatment plan used for this patient.

Results: All plans complied with our planning strategy and met, with good accordance, the objectives for the PTV (D98% > 93%, V105% < 20 %), RLN_CTVs (D98% > 95%) and CTV_IMN (D98% > 90 %), except for two plans which did not meet the criteria for CTV_IMN. Consistent values for the mean heart dose (range 1.3 - 1.5 Gy) were registered. Considerable deviations in the mean dose (range 11.5-13.2 Gy) and V16Gy (range 29.8 - 34.8 %) for the left lung, were noted. A summary of the obtained results for all the OAR is shown in Figure 2.