Early results of the French multicenter, randomized SHARE trial comparing whole breast irradiation versus accelerated partial breast irradiation in postmenopausal women with early-stage low risk breast cancer: Analysis of toxicity and cosmetic outcomes.

• DOI: 10.1200/jco.2025.43.16_suppl.514
• Publication Date: 2025-05-28T16:43:03Z
• Authors: Yazid Belkacemi; Isabelle Gabelle ...; Marie-Cecile Le D...; Clemence Leguillette; Kamel Debbi; Adeline Petit; Philippe Guilbert; Julien Geffrelot; Christian Carrie; Eleonor Rivin Del...; Chantal Hanzen; Claire Brunaud; Isabelle Lecouillard; Nicolas Magné; Emilie Bogart; Guillaume Auzac; Thomas Lacornerie; Jerome Lemonnier; Celine Bourgier; Eric Lartigau

514 Background: Locoregional management of early stage breast cancer (BC) has evolved from maximal tolerable to minimal effective therapies. Significant advancements in radiation therapy (RT), such as limited target volumes and hypofractionation, have led accelerated partial irradiation (APBI). This study reports on toxicity cosmetic outcomes APBI post-menopausal women with unifocal pT1-N0-M0 invasive BC. Methods: The SHARE trial (NCT01247233) is a non-inferiority, multicenter, randomized comparing local control versus Whole Breast Irradiation (WBI). Eligible patients were postmenopausal over 50 years who had lumpectomy surgical margins > 2mm. Only at least 4-5 clips placed the tumor bed during surgery eligible. Patients receive either WBI (50Gy 25 fractions (fr) optional 16Gy-boost or 40Gy 15 fr, 42.5Gy 16fr) (38.5Gy 10fr twice daily). Primary endpoint was recurrence. Secondary endpoints included grade >2 (NCI-CTCAE-v4) (good/excellent intermediate/poor) evaluated by both doctors, follow-up time. We estimated cumulative incidences (CI) using Kalbfleisch-Prentice method due competing events, cause-specific Hazard Ratios (cs-HR APBI/WBI ) Cox models adjusted stratification factors. Results: Among 1006 (503 per arm) enrolled between December-2010 July-2015, median 5.8 years, 28 deaths 11 recurrences reported. risk severe appeared significantly reduced APBI-arm when considering all type =0.74, [95%-CI: 0.61-0.89], p=0.001; 3-year CI=45% [41-49] vs 36% [32-40] APBI), only skin (cs-HR=0.55 [0.44-0.70], p<0.001; CI=36% 21% [18-25], respectively). Conversely, for non toxicities, less toxic: cs-HR =2.06 (1.49-2.86), p<0.001). observed no significant difference patient-reported results: =1.08 (0.85-1.37), p=0.54. Findings similar doctor-evaluated results. Rib fractures incidence nearly double compared WBI. Conclusions: showed that associated skin-related toxicities WBI, outcomes. toxic concerning non-skin toxicity, mainly fibrosis. question currently remains open practical level how consider context widespread adoption “Fast Forward” regimen low Clinical information: 2010-A00243-36 .