S230
Clinical - Breast
ESTRO 2026
Long term results of Partial Breast Irradiation with External Beam Radiotherapy Miguel Angel Souto Del Bosque 1 , Cindy Sharon Ortiz Arce 2 , Jorge Anselmo Vázquez Delgado 3 , Alejandro Olmos Guzmán 4 1 Radiotherapy, Christus Muguerza, Monterrey, Mexico. 2 Radiotherapy, UMAE 25 IMSS, Monterrey, Mexico. 3 Radiotherapy, Breast Cancer Foundation (FUCAM), Mexico, Mexico. 4 Radiotherapy, UMAE 1, IMSS, León, Mexico Purpose/Objective: The lack of radiation centers and overcrowded public health institutions produce long waiting time, so is imperative encourage used hypofractionated and ultra-hypofractionated treatments as Partial Breast Irradiation (PBI)as an strategy to reduce waiting times to radiotherapy, then we decided to analyze Overall Survival (OS) and Recurrence Free Survival (RFS) of patients treated with PBI Material/Methods: We reviewed clinical records of patients treated with radiotherapy from January 2013 to December 2019; according to schedule of radiotherapy, patients were assigned to intervention group, treated with partial breast irradiation or control group, treated with hypofractionated schedule of radiotherapy. Survival analysis was performed using Kaplan-Meier curves and compared with Log-Rank test, using Graph Pad Prism v 10.0.3 Statistical software. Study was retrospectively registered and approved by ethical and scientific boards of Mexican Social Security Institute, number CNIC R-2024-785-076. Results: A total of 214 cases were included, mainly Stage I, Luminal molecular profile. Control group was mainly treated with dose of 40 Gy/15 daily fractions and partial breast irradiation group was treated the most with 30 Gy/5 daily fractions. Only 10% of cases had recurrences in both groups, mainly systemic; some of the patients with regional recurrences had high risk molecular profile because Her2/neu overexpression or luminal B profile. With respect of mortality, 2% of patients in control group dead because non-breast cancer, including secondary malignancies as pancreatic cancer, anal cancer, and cholangiocarcinoma and 2%; of cases in APBI group dead, one patient for a second malignancy and only one patient for breast cancer progression, without differences between groups.Average follow up was 41 months, with a maximum of 107 months; we observed non-differences between PBI and control group regarding OS with a HR of 0.750 (95% CI 0.103 – 5.438) and in breast cancer specific survival (BCSS). Median survival was undefined for both groups (Fig 1).
integrated boost technique. Patients were treated with a 2D (dimensional) or 3D technique on a linear accelerator. Cosmetic outcome was reported by the physician and patients at baseline and at 3 years after radiotherapy using NSABP/ HARVARD/RTOG breast cosmesis and EORTC grading scale, respectively. Cosmetic outcome was categorised as excellent/good and fair/poor. Fisher's exact test was used to compare the differences in the three radiotherapy schedules. All statistical tests were two sided, and p values of <0.05 was taken as significant. Results: Between June 2015 and December 2023, 600 breast cancer patients were included; 141, 308 and 151 in the 3 week, 2 week and 1 week schedules, respectively. Patient characteristics were balanced in the three schedules. Boost was delivered in 81 (57.5%), 168 (54.5%) and 109 (72.0%) patients in the 3 week, 2 week and 1 week schedules, respectively. Boost volume was 218.56±36.27, 212.62±40.03 and 223.62±39.78 in 3 week, 2 week and 1 week schedules, respectively. Modalities used to deliver boost were electrons and photons in 23 (28.4%), 47 (28.0%) and 31 (26.5%); and 58 (71.6%), 121(72.0%) and 78 (71.5%) patients in 3 week, 2 week and 1 week schedules, respectively. Median follow up was 42 months (range 24-51 months). At 3 years, physician reported cosmetic outcome was excellent/good and fair/poor in 131 (93.0%), 294 (95.5%) and 125 (82.8%), and 10 (7.0%), 14 (4.5%) and 26 (17.2%) patients (p=0.005) in 3 week, 2 week and 1 week schedules, respectively. Patient reported outcome was excellent/good and fair/poor in 130 (92.0%), 301 (97.8% and 142 (94.0%), and 11 (8.0%), 7 (2.2%) and 9 (6%) patients (p=0.070) in 3 week, 2 week and 1 week schedules, respectively. Conclusion: Clinician reported cosmetic outcome was better with the 2 week radiotherapy schedule. Patients reported cosmetic outcome was comparable in the three radiotherapy schedules. References: 1. Yadav BS, Dahiya D, Gupta M et al. Preliminary results of hypofractionated radiotherapy in breast cancer in Chandigarh, India: single-centre, non- inferiority, open-label, randomised, phase 3 trial. Lancet Reg Health Southeast Asia 2024, 24https://doi.org/10.1016/j.lansea.2024.1003922. Yadav BS, Dahiya D, Kanan P et al. HYPofractionated Adjuvant RadioTherapy in 1 versus 2 weeks in high-risk patients with breast cancer (HYPART): a non-inferiority, open-label, phase III randomised trial. Trials. 2024 Jan 2;25(1):21. doi: 10.1186/s13063-023-07851-7. PMID: 38167339; PMCID: PMC10763219. Keywords: Hypofractionation, Cosmetic outcome, Digital Poster 1065
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