S2962
Late-Breaking
ESTRO 2026
BCS, pT1N0, non-lobular, grade 1-2, estrogen receptor (ER) ≥ 10%, HER2 normal, margin ≥ 2mm) between PBI versus no PBI. Patients declining randomization could self-select no PBI. Annual follow-up included morbidities and mammography. Endocrine treatment (ET) was recommended for pT1c and/or grade 2. Primary endpoint was 5-year local recurrence (LR) expected to be 2% and accepted up to 4% without PBI. An interim analysis was planned when 200 patients had 2-year follow-up (FU). Results: Accrual started 2018 and paused November 2023, at the interim analysis, and terminated November 2024 with 251 patients randomized to RT (+RT), 273 randomized to no RT (-RT) and 278 self-selecting no RT (S-RT), total 802 patients. Median age was 68 years (range 60-86). Grade 2 was seen in 368 patients, 421 had pT1c and 777 were ER 90-100%.Comparing +RT with -RT showed no differences in clinical parameters, comparing randomized to non-randomized showed lower BMI for S-RT, p<0.01. In February 2026, estimated median potential FU was 4 years. Overall, 446 patients started ET (148 +RT, 154 -RT, 144 S-RT), whilst 98 declined ET at baseline. ET adherence for those starting was 62.1% (95% CI, 57.3-67.4) at 4.5 years. Isolated LR was detected in 36 patients: four +RT (two had declined RT), 15 -RT, and 17 S-RT (Figure 1, per-protocol cohort). Among -RT patients, three had LRR, and two (one -RT and one S-RT) had LR combined with distant recurrence. The 5-year cumulative incidence of LR (with competing risks) in the ITT population was 1.9% (0.5-5.3) (+RT), 9.8% (5.9-14.9) (- RT) and 8.2% (4.5-13.3) (S-RT). For irradiated versus non-irradiated patients it was 1.5% (0.3-5.1) versus 9.1% (6.3-12.5). Contralateral BC was reported in one (+RT), six (-RT) and five patients (S-RT), respectively. Distant failure as first event was seen in two (+RT), one (-RT) and one patient (S-RT), and death as first event in five (+RT), four (-RT), and five patients (S-RT). Morbidities showed no differences, except dyspigmentation with PBI (p<0.01). Conclusion: PBI in selected BC patients is highly effective in avoiding local recurrence with modest morbidity
Keywords: Breast cancer, randomised controlled trial
Proffered Paper 5506
Individual patient data meta-analysis of anti-EGFR monoclonal antibodies in locoregionally advanced head and neck cancers: final analysis of MACH- EGFR Pierre Blanchard 1 , Maurice Cheugoua-Zanetsie 2 , Imene Deneche 2 , Jonathan Harris 3 , David I Rosenthal 4 , Mitchell Machtay 5 , Sue S Yom 6 , Jesper G Eriksen 7 , Jens Overgaard 7 , Kumar Prabhash 8 , Vanita Noronha 8 , Narayanan G Iyer 9 , Khee C Soo 9 , James A Bonner 10 , Jordi Giralt 11 , Andreas Dietz 12 , Ricard Mesia 13 , Antonio Rueda 14 , Oliver Riesterer 15 , Tania Crombet 16 , Anne Aupérin 2 1 Radiation Oncology, Gustave Roussy, Villejuif, France. 2 Biostatistics and Epidemiology, Gustave Roussy, Villejuif, France. 3 NRG Oncology Statistics and Data Management Center, NRG, Philadelphia, USA. 4 Radiation Oncology, UT MD Anderson Cancer Center, Houston, USA. 5 Radiation Oncology, Penn State Milton S Hershey Medical Center, Hershey, USA. 6 Radiation Oncology, University of California, San Francisco, USA. 7 Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark. 8 Medical Oncology, Tata Memorial Centre, Mumbai, India. 9 Head and Neck Surgery, Singapore General Hospital & National Cancer Centre, Singapore, Singapore. 10 Radiation Oncology, University of Alabama at Birmingham, Birmingham, USA. 11 Radiation Oncology, Vall d'Hebron Hospital. Universidad Autonoma de Barcelona, Barcelona, Spain. 12 Head and Neck Surgery, University of Leipzig, Leipzig, Germany. 13 Medical Oncology, Institut Català d'Oncologia: Badalona, Badalona, Spain. 14 Medical Oncology, Hospital Regional Universitario de Málaga, Malaga, Spain. 15 Radiation Oncology, University Hospital Zurich, Zurich, Switzerland.
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