ESTRO 2022 - Abstract Book

S853

Abstract book

ESTRO 2022

breast shrinkage assessed by clinicians in merely 5.5% of patients after 40 Gy/15 fractions compared with 6.8% after 26 Gy/5 fractions. Real life evidence, e.g., based on prospective cohorts and registration studies can assist in the broad introduction of ultra- hypofractionation. However, I strongly advocate that further randomised research in this field should focus on topics such as immediate breast reconstruction, simultaneous integrated boost, preoperative RT, combinations with other treatments and nodal irradiation, instead of spending the little money that is available for pure academic radiation oncology research to repeat was has already been demonstrated.

SP-0978 Nodal irradiation

C. Coles 1

1 University of Cambridge, Department of Oncology, Cambridge, United Kingdom

Abstract Text Moderate hypofractionation was adopted internationally in the 1970’s and 1980’s as a solution for scarce resource for breast radiation therapy (RT). This was based on the theoretical Ellis isoeffect formula and was introduced without testing in clinical trials with a lack of RT quality assurance [1]. Unfortunately, this resulted in many patients with breast cancer suffering serious late normal tissue toxicity, including brachial plexopathy following nodal RT. It became apparent that a vital component in hypofractionation is reduction of total dose as the dose per fraction is increased and several randomised trials based on the linear-quadratic formula ensued [1]. This presentation will review the current evidence for moderately hypofractionated breast RT [2-4] and highlight on-going Danish and French trials that will add to this evidence. It will then discuss 5-fraction (5F) RT [5] and describe the FAST- Forward nodal sub-study design (interim results have been submitted as a late-breaking abstract to ESTRO 2022). On-going recruiting 5F breast and nodal RT randomised trials in Canada and India will also be covered. Finally, current guidelines and consensus statements for breast nodal RT will be presented [6-7]. 2. Haviland JS, Mannino M, Griffin C, et al. Late normal tissue effects in the arm and shoulder following lymphatic radiotherapy: Results from the UK START (Standardisation of Breast Radiotherapy) trials. Radiother Oncol 2018; 126(1): 155-62. 3. Wang SL, Fang H, Song YW, et al. Hypofractionated versus conventional fractionated postmastectomy radiotherapy for patients with high-risk breast cancer: a randomised, non-inferiority, open-label, phase 3 trial. Lancet Oncol 2019; 20(3): 352-60. 4. Coles C, Griffin C, Kirby A, et al. Abstract GS4-05: Dose escalated simultaneous integrated boost radiotherapy for women treated by breast conservation surgery for early breast cancer: 3-year adverse effects in the IMPORT HIGH trial (CRUK/06/003). Cancer Research 2019; 79(4 Supplement): GS4-05-GS4-. 5. Murray Brunt A, Haviland JS, Wheatley DA, et al. Hypofractionated breast radiotherapy for 1 week versus 3 weeks (FAST-Forward): 5-year efficacy and late normal tissue effects results from a multicentre, non-inferiority, randomised, phase 3 trial. Lancet 2020; 395(10237): 1613-26. 6. Lewis P, Brunt AM, Coles C, Griffin S, Locke I, Roques T; Breast Radiotherapy Consensus Working Group. Clin Oncol (R Coll Radiol). Moving Forward Fast with FAST-Forward. Clin Oncol (R Coll Radiol) 2021 Jul;33(7):427-429 7. Meattini I, Becherini C, Boersma L, Kaidar-Person O, Nader Marta O, Montero A, Offersen BV, Aznar MC, Belka C, Brunt AM, Dicuonzo S, Franco P, Krause M, MacKenzie M, Marinko M, Marrazzo L, Ratosa I, Scholten A, Senkus E, Stobart H, Poortmans P and Coles CE. European Society for Radiotherapy and Oncology (ESTRO) Advisory Committee in Radiation Oncology Practice (ACROP) consensus recommendations on patient selection and dose/fractionation for external beam radiation therapy in early breast cancer. Lancet Oncol. 2022 Jan;23(1):e21-e31. References 1. Yarnold J, Bentzen SM, Coles C, Haviland J. Hypofractionated whole-breast radiotherapy for women with early breast cancer: myths and realities. Int J Radiat Oncol Biol Phys 2011; 79(1): 1-9.

SP-0979 Chest wall irradiation with or without breast reconstruction

I. Meattini 1

1 University of Florence, Department of Experimental and Clinical Biomedical Sciences "M. Serio", Florence, Italy

Abstract Text Moderate hypofractionation for chest wall irradiation is under-represented within randomised trials. Mastectomy was not included in the Ontario trial and represented less than 10% of patients in the START B trial. Although it has been established as standard of care in some countries for many years, the overall uptake of moderate hypofractionation for chest wall irradiation is still low in Europe. There is no biological reason to assume that the efficacy and toxicity profile observed after breast conserving surgery does not apply to postmastectomy irradiation. Wang and colleagues reported the results of