ESTRO 2024 - Abstract Book

S5937

RTT - Treatment planning, OAR and target definitions

ESTRO 2024

overlap lengths. For CSI VMAT planning, employing the auto feathering algorithm and ensuring field overlap lengths surpass 5 cm are recommended to enhance plan resilience.

Keywords: craniospinal irradiation, plan robustness, VMAT

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Deep-inspiration breath-hold for right breast:impact on the organs at risk and on the treatment time

Damien Fuligno

HFR Fribourg, Radiation Oncology, Fribourg, Switzerland

Purpose/Objective:

This retrospective study aims to determine and quantify the advantages and disadvantages of a treatment with deep inspiration breath-hold (DIBH) compared to a treatment with free-breathing (FB) technique for the irradiation of patients with right breast cancer.

Material/Methods:

Thirty patients were treated on the right breast with a dose of 42.56 Gy in 16 fractions, eleven with FB and nineteen with DIBH technique. The use of these 2 techniques was due to an institutional practice change. The treatment plans were all carried out with the Eclipse TPS (version 16.1.4) and the Acuros algorithm (Varian), using two 6MV opposed tangential fields with sliding window-based IMRT. For the first day of treatment, depending on the patient anatomy and treatment complexity, we performed kV + CBCT or only kV. For the following sessions (2-16th session), we performed only kV images. We analyzed for day 1 and day 16 the average and maximum doses received by the heart and the liver. For the right lung, we recorded the volumes irradiated at V5 Gy, V20 Gy and the mean dose.

Results:

Compared to FB, for DIBH treatments, the CBCT performed on day 1 doubles the patient immobilization time on the treatment table, while for the others treatment sessions, the immobilization time is only increased by 43 seconds on average. Results show that the maximum dose received by the heart is reduced by a factor of 1.6 (p-value = 0.02) and the average dose by a factor 1.25 (p-value = 0.05). The maximum dose received by the liver is reduced by a factor 2.4 (p-value = 0.002). However, the dose received by the right lung is very similar, showing no statistically significant difference. (p-value = 0.54 for V20).