S330
Clinical - Breast
ESTRO 2026
Calgary, AB, Canada. 10 Division of Radiation Oncology, Department of Surgery, University of British Columbia, Vancouver, BC, Canada. 11 Department of Radiation Oncology, BC Cancer—Vancouver, Vancouver, BC, Canada. 12 Department of Oncology, Division of Radiation Oncology, McGill University, Montreal, QC, Canada. 13 Division of Radiation Oncology, McGill University Health Centre, Montreal, QC, Canada. 14 Department of Oncology, Faculty of Health Sciences, McMaster University, Hamilton, ON, Canada. 15 Department of Radiation Oncology, Odette Cancer CEntre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada. 16 Department of Radiation Oncology, National University Cancer Institute, National University Hospital, Singapore, Singapore. 17 Department of Medicine, Yong Loo Lin School of Medicine, Singapore, Singapore Purpose/Objective: Ultrahypofractionation (26 Gy in 5 fractions) has demonstrated clinical non-inferiority compared to moderate hypofractionation (40 Gy in 15 fractions) for adjuvant whole breast radiotherapy (WBRT) in early- stage breast cancer.1 Hence, we conducted a cost- effectiveness analysis (CEA) from a Canadian public healthcare perspective to quantify the economic value of adopting ultrahypofractionation. This report presents Phase I results based on historic, published Canadian data from a single institution. Material/Methods: We constructed a decision-analytic cost-utility model to compare adjuvant 26Gy vs 40Gy in early-stage breast cancer. We calculated the direct costs per radiation fraction at the London Health Sciences Centre in 2020,2 which included radiotherapy delivery (CT simulation, planning, quality assurance, and linear accelerator depreciation). Indirect costs were added to the calculation, including acute radiation dermatitis (ARD) management and nursing time (Grade 1 dermatitis requiring 15 minutes weekly, Grade 2-3 requiring 30-60 minutes). ARD rates were extracted from the FAST-Forward trial substudy (2016) using CTCAE v4.03.3 Utilities were derived using the Vilsbøll et al. mapping algorithm that converts dermatitis severity scores to EQ-5D values and were applied over the 6-week acute period. The utility decrement for Grade 2–3 vs none was assumed to be 0.10 (no dermatitis: 0.95; Grade 2-3 dermatitis: 0.85) as per the methodology described in Tse et al.4 Willingness-to- pay threshold was CAD $50,000/QALY. One-way sensitivity analysis will be used to test parameter uncertainty. Results: FAST-Forward trial demonstrated Grade 2–3 ARD in 32.1% vs 41.9% for 26Gy/5# vs 40Gy/15#, respectively. With this modification, our analysis showed total costs of CAD $893 vs 1,381 per patient. We noted an ICER of
CAD -$4,318 per QALY gained, resulting from an incremental cost of CAD -$488 and an incremental effectiveness gain of +0.001131 QALYs (0.946296 vs 0.945165). Net monetary benefit was CAD $553.5 per patient. For the London Health Sciences Centre (358 patients annually), savings would reach CAD ~$190,000 yearly. Ontario-wide implementation (4,226 patients) could save CAD $2.23 million annually. Sensitivity analyses in Phase II will test cost- effectiveness across all parameter ranges. Conclusion: Phase I analysis demonstrated that ultrahypofractionated WBRT yields significant cost savings and improved resource utilization compared with moderate hypofractionation when incorporating utility and ARD management costs, aligning with previous cost-minimization studies. Phase II will include a probabilistic sensitivity analysis using multicentre prospective data to validate economical dominance of ultrahypofractionation and support its adoption as standard of care. References: Brunt, A. M., et al. FAST-Forward: 5-year efficacy and late normal tissue effects results from a multicentre, non-inferiority, randomised, phase 3 trial. Lancet 2020, 395(10237), 1613–1626. Yaremko, H. L., et al. Cost
Minimization Analysis of Hypofractionated Radiotherapy. Curr. Oncol. 2021, 28(1), 716–
725. Brunt, A. M., et al. Acute skin toxicity associated with a 1-week schedule of whole breast radiotherapy compared with a standard 3-week regimen delivered in the UK FAST-Forward Trial. Radiother. Oncol. 2016, 120(1), 114–118. Tse, S. S. W., et al. Cost-Effectiveness Analysis of Mepitel Film for Prevention of Acute Radiation Dermatitis in Breast Cancer: A Canadian Healthcare Perspective. Breast Cancer Res.Treat. (under review). Keywords: Early stage breast cancer, health economics Safety and Tolerance of Adjuvant Radiotherapy after Oncoplastic Breast Surgery: Impact of Monolateral vs Bilateral Procedures Vera Cirnigliaro 1 , Edy Ippolito 1,2 , Sara Reina 1 , Paolo Orsaria 3 , Antonella Grasso 3 , Sonia Silipigni 1 , Salvatore Minuti 2 , Paola Martucci 1 , Roberto Conti 1 , Paolo Matteucci 1 , Carlo Greco 1,2 , Michele Fiore 1,2 , Vittorio Altomare 3 , Sara Ramella 1,2 1 Operative Research Unit of Radiation Oncology, Fondazione Policlinico Universitario Campus Bio- Medico, Rome, Italy. 2 Research Unit of Radiation Digital Poster Highlight 4608 Oncology, Università Campus Bio-Medico, Rome, Italy. 3 Department of Breast Surgery, Fondazione Policlinico Universitario Campus Bio-Medico, Rome, Italy
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