ESTRO 2023 - Abstract Book

S1830

Digital Posters

ESTRO 2023

1005. The LINAC output was measured to evaluate deliverability and quality of the plans based on the gamma index tool.

Results Table 2 shows the dosimetric parameters obtained with dMLC technique compared with the three constraint protocols: DBCG HYPO trial, RTOG1005 and in-house constraints. The results were separated between left and right breast cancer patients. Most results were under the constraints required from any of the protocols. For LADCA, 5 patients out of 15 received more than 17Gy in maximum dose. However, D2cc < 15Gy was achieved for all the patients. The mean conformity index achieved was 0.75 ± 0.07. The mean monitor units per plan was about 290±40. The large segments sizes encompassing the entire breast height are visible in figure 1. Regarding the QA measurements, all plans passed the 3%/3mm gamma index criteria.

Conclusion The main objectives of this work were achieved. The parameters defined in table 1 limited considerably the plan modulation and thus ensuring a fast and robust treatment delivery. This is particularly visible in the low number of monitor units (290 ± 40) and in the large segments sizes. Regarding the constraints achieved whether they were suitable or not, based on published literature ( Thomsen M.S. et al, CTRO 2021; Arbor A. et al, RTOG1005 2013; Piroth M.D. et al, Strahlenther Onkol 2019; Fogliata A. et al, IJROBP 2017; Koivumäcki T. et al, R&O 2016; Marrazzo L. et al, Physica Medica 2022 ), we believe this technique offers good dosimetric