ESTRO 2024 - Abstract Book

S544

Clinical - Breast

ESTRO 2024

1363

Digital Poster

Left breast cancer dosimetry with Accuray VOLO TM Ultra optimizer: a comparison with DIBH

Patrizia Urso, Nathan A Corradini, Giorgio Ballerini, Laura Negretti, Cristina Vite, Alessandra Franzetti-Pellenda

Gruppo Ospedaliero Moncucco, Radiotherapy, Lugano, Switzerland

Purpose/Objective:

Even if the radiotherapy for breast cancer is well-known to improve local control and overall survival, clinically induced late side effects on heart and lung for left breast cancer treatments is a serious issue for the health of patients [1]. Aim of this study is the evaluation of dosimetric objectives, in terms of target coverage and organ at risk (OAR) sparing, obtained by the Accuray Precision v.3 treatment planning system (TPS), for Radixact and TomoTherapy systems, recently upgraded with the VOLO TM Ultra optimizer. Results intend to be compared to the dosimetry related to the Deep Inspiration Breath Hold technique (DIBH) reported in the scientific literature, considered one of the most effective approaches in the reduction of the dose to heart and ipsilateral lung [2].

Material/Methods:

The analysis deals with the dosimetric results related to the whole set of women treated to the whole breast at the Gruppo Ospedaliero Moncucco, starting from the introduction of VOLO TM Ultra (i.e. from February 2022 to September 2023).

The two techniques, direct (TD) and helical (TH), were used depending on geometry and complexity of the target, preferring as much as possible the TD technique in order to reduce low dose to the OARs.

Prescription dose to the whole breast was 50 Gy/25 fx or 42.4 Gy/16 fx. A minimum coverage of 95% of PTV volume by at least 95% of prescribed dose and the maximum volume covered by 107% of prescription dose was required to be less than 1 cc. Constraints to OARs were based on both the international and internal guidelines.

Results:

The whole sample included 66 treatment plans, 39 performed using TD (26 with 42.4 Gy/16 fx and 13 with 50 Gy/25 fx) and 27 using TH (11 with 42.4 Gy/16 fx, 16 with 50 Gy/25 fx). The TD plans had a mean beam on time of 168.8±26.5 sec, while TH were about 400.6±74.7 sec, with an average gantry period of 17.2±3.5 sec. On the average, mean dose covering the planning target volume (PTV) was 99.4% for TD and 99.9% for TH, V 95% =96.1±1.7% and 95.9±1.4%, with V 107% =0.2±0.3 cc and 0.4±1.1 cc for TD and TH, respectively. Regarding dose to the OARs, detailed results are described in table 1, reported as average and standard deviation. Briefly, the heart mean doses, for the two fractionations 42.4 Gy/50 Gy, were 1.0±0.5/1.1±0.4 Gy and 1.7±0.7/2.0±0.7 Gy for TD and TH respectively, resulting comparable with the DIBH values reported in the recent meta-analysis [3], ranging between 0.9 and 2.7 Gy. Similarly, for ipsilateral lung the mean dose was 4.4±1.1/5.2±0.9 Gy and