ESTRO 2023 - Abstract Book

S171

Saturday 13 May

ESTRO 2023

In particular, for WB RT, D50% for level 1 was 46% (1.3-99.2%), WB plus SIB (46 (1.3-99.2) (Fig 1C). Similar variation was observed for internal mammary nodes and for other dose metrics (data not shown).

Conclusion There is considerable variation between patients and between centres in the incidental dose to the axilla and the ALTJ region. This study highlights the necessity of investigating individual dose distributions when understanding the link between dose and toxicity in breast cancer patients. The proposed method demonstrates the feasibility of using deformable image registration techniques to facilitate efficient retrospective assessment and validation of newly identified regions of interest, without the need for resource-intensive contouring of hundreds of patients. Further work is planned in the full REQUITE cohort to identify anatomical subregions particularly sensitive to dose, and link this with late arm/shoulder toxicity. References 1. Gross IJROBP 2019 PD-0236 Patterns of recurrence in breast cancer patients after nipple-sparing and skin-sparing mastectomy L. Alvarado 1 , D. Mahmoud 1 , R. Franco 1 , P. Poortmans 2 , O. Kaidar-Person 3 , T. Hijal 1 1 McGill University Health Centre, Division of Radiation Oncology, Montreal, Canada; 2 Iridium Kankernetwerk, Division of Radiation Oncology, Wilrijk-Antwerp, Belgium; 3 Chaim Sheba Medical Center, Breast Radiation Unit, Tel-Hashomer, Israel Purpose or Objective Reports of residual breast tissue after nipple-sparing (NSM), and skin-sparing mastectomy (SSM), have raised concerns regarding safety as well as interest in determining patterns of recurrence in patients undergoing these trending surgical techniques, to better tailor systemic and local treatments. Materials and Methods