ESTRO 2024 - Abstract Book

S699

Clinical - Breast

ESTRO 2024

With a 6 years median follow-up, in CANTO, radiation therapy was not associated with an increased risk of cardiac events whereas history of cardiac event, trastuzumab, and obesity at enrolment were.

Further analysis with longer follow up integrating adjudication of cardiac events based on the national health system registry will be performed.

Keywords: Cardiac toxicity, Prospective longitudinal study

References:

1. Ines Vaz-Luis, Paul Cottu, Christel Mesleard et al UNICANCER: French prospective cohort study of treatment related chronic toxicity in women with localised breast cancer (CANTO), ESMO Open, Volume 4, Issue 5, 2019, e000562, ISSN 2059-7029, https://doi.org/10.1136/esmoopen-2019-000562.

2945

Digital Poster

Simultaneous integrated boost in breast radiotherapy: Comparison of delineation methods

Jennifer Trousdell, Fran Duane, Orla McArdle

St Luke's Radiation Oncology Network, SLRON, Dublin, Ireland

Purpose/Objective:

Sequential boost to the tumour bed is associated with reduced risk of recurrence in high-risk breast cancer treated with breast conserving surgery 1 . Two large randomised controlled trials have recently demonstrated acceptable toxicity profiles for simultaneous integrated boost 2,3 . These trials used varying methods of delineating boost volumes. There is evidence to suggest that the volume of breast tissue irradiated to ≥40Gy is predictive of breast fibrosis 4 . Published data suggest D ≥40Gy of ≥177cm3 and ≥426cm3 correlate with 5% and 10% risk respectively of grade 2 or 3 breast induration. This highlights the importance of minimising boost volumes. We designed a study to assess the boost volume treated using various delineation protocols.

Material/Methods:

Twenty consecutive patients who received radical breast radiotherapy with boost were identified from January 2022. Data were collected for patient baseline tumour and treatment characteristics. Breast boost volumes were delineated according to four protocols; two trial protocols and two institutional protocols. Trial boost volumes included; Import High Trial; (Clips + seroma) = CTV + 5mm = PTV 2 and NRG Trial; (Clips + seroma) + 1cm= CTV +7mm = PTV 3 . Institutional boost volumes included; current institutional guidelines; (Clips + seroma) + 5mm = CTV +5mm = PTV and alternative institutional guidelines; (Clips + seroma) + 5mm = CTV + 7mm = PTV.