ESTRO 2023 - Abstract Book

S625

Monday 15 May 2023

ESTRO 2023

Figure 2: Forest plot. Pooled HRs for overall survival comparing high to low-volume radiotherapy facilities for twelve cancer types; 18 studies were included in the meta-analysis; Tchelebi et al represents one study Conclusion An association between radiotherapy treatment volume and patient outcomes exists for most cancer types. Centralisation of radiotherapy services should be considered for cancer types with the strongest volume outcome association such as HNCs but the impact on equitable access to services needs to be explicitly considered. Very low volume practices should be consolidated or partnered with established HVRFs to support quality improvement. OC-0758 HypoG01:UNICANCER phase 3 trial of locoregional hypo vs normo fractionated RT in early breast cancer S. Rivera 1 , E. Karamouza 2 , Y. Kirova 3 , S. Racadot 4 , M. Benchalal 5 , J.B. Clavier 6 , C. Charra Brunaud 7 , M. Fouche-Chand 8 , D. Argo-Leignel 9 , K. Peignaux 10 , A. Benyoucef 11 , D. Pasquier 12 , P. Guilbert 13 , J. Blanchecotte 14 , A. Tallet 15 , A. Petit 16 , G. Bernadou 17 , X. Zasadny 18 , C. Lemanski 19 , J. Fourquet 20 , N. Bonnet 21 , A. Lamrani-Ghaouti 21 , M. Bergeaud 21 , G. Auzac 1 , S. Michiels 2 1 Gustave Roussy, Radiotherapy, Villejuif, France; 2 Gustave Roussy, Statistics, Villejuif, France; 3 Curie, Radiotherapy, Paris, France; 4 Léon Bérard, Radiotherapy, Lyon, France; 5 Eugène Marquis, Radiotherapy, Rennes, France; 6 Paul Strauss, Radiotherapy, STRASBOURG, France; 7 Institut de Cancérologie de Lorraine, Radiotherapy, Nancy, France; 8 Antoine Lacassagne, Radiotherapy, Nice, France; 9 Hôpital du Scorff, Radiotherapy, Lorient, France; 10 G F Leclerc, Radiotherapy, Dijon, France; 11 Henri Becquerel, Radiotherapy, Rouen, France; 12 Centre Oscar Lambret, Radiotherapy, Lille, France; 13 Jean Godinot, Radiotherapy, Reims, France; 14 ICO - Site Paul Papin, Radiotherapy, Angers, France; 15 Paoli Calmettes, Radiotherapy, MARSEILLE, France; 16 Bergonié, Radiotherapy, BORDEAUX, France; 17 Centre de recherche oncologique clinique 37, Radiotherapy, CHAMBRAY LES TOURS, France; 18 Clinique Chenieux, Radiotherapy, LIMOGES, France; 19 ICM Val d'Aurelle, Radiotherapy, MONTPELLIER, France; 20 Centre hospitalier de Lens, Radiotherapy, Lens, France; 21 UNICANCER, UNITRAD, Kremlin Bicêtre, France Purpose or Objective Hypofractionated (HF) radiation therapy (RT) is the standard regimen for whole breast RT but normofractionated (NF) RT using 50 Gy/25 fr is still standard for loco-regional early breast cancer (EBC) due to possible higher risk of morbidity. HypoG- 01, a UNICANCER, non-inferiority, open-label, multicenter, randomized phase III trial (NCT03127995), conducted in parallel with the DBCG Skagen trial 1, assessed if HF RT with 40 Gy/15 fr (2.67 Gy/fr) would not result in more arm lymphedema over time than NF RT 50 Gy/25 fr (2.0 Gy/fr). Materials and Methods Patients (pts) were ≥ 18 years old operated for T1-3, N0-3, M0 breast cancer. All pts received nodal and thoracic wall or breast RT. Tumor-bed boosts and nodal levels treated were decided according to local guidelines, target volumes delineated according to ESTRO consensus, RT techniques at the investigators discretion and each center validated a dummy run. The primary endpoint was time to occurrence of arm lymphedema after RT defined as ≥ 10% increase in arm circumference 15 cm proximal and/or 10 cm distal of the ipsilateral olecranon relative to baseline, compared to the contralateral circumference. The primary statistic test was stratified one-sided logrank test: 5% significance level in per-protocol population (PPP) with a pre-specified non-inferiority margin of 1.545. Range of shoulder motion (ROM) impairment was a reduction ≥ 25° in active abduction or flexion. Results 1265 pts were randomized to NF or HF RT from Sep 2016 to Mar 2020 with 1221 in the PPP (HF group 614 pts (50.3%); NF group 607 (49.7%)), 5 consent withdrawn and 39 major deviations. Median age was 58 years (range 23-91), surgery included mastectomy (501 pts; 45%) and axillary clearance (921 pts; 82.8%) with a mean number of 12 removed nodes. Sequential (67.8%) or integrated (32.2%) tumor-bed boost was used in 596 pts (48.8%). With a median follow-up of 3.1 years (IQR 3.1- 3.2), 251 lymphedemas occurred among the 1113 pts with baseline and end of treatment lymphedema measurements. HF was non-inferior to NF RT in terms of risk of lymphedema (HR=1.07; 90% CI 0.86-1.34, non-inferiority p=0.003; Fig 1). The 3-year rate of ipsilateral arm lymphedema was 24.1% (95% CI 20.3-28.4) in HF group vs 22.6% (95% CI 18.9-26.9) in NF. The intention-to-treat (ITT) analysis led to a similar HR=1.08 (90% CI 0.86-1.35; non-inferiority p=0.004). ROM impairment occurred in 256 pts with a time to ROM impairment HR=0.91 (90% CI 0.73-1.13) in HF vs NF. In ITT, 23 pts had at least 1 SAE (HF: 13, NF: 10), maximum grade 3, mostly not treatment-related. Further secondary endpoints results will be presented at the meeting. Proffered Papers: Late-breaking Papers