S338
Clinical - Breast
ESTRO 2026
radiotherapy and systemic-treatment. Radiotherapy consisted of 40.5 Gy in 15 fractions to whole breast and regional nodes, with a simultaneous integrated boost up to 54 Gy to the macroscopic tumor using 18- FDG-PET-CT for contouring and VMAT technique for planning. Daily CBCT and Surface guided RT was used for daily verification. Concomitant systemic therapy included Paclitaxel–Carboplatin for TN and Pertuzumab–Trastuzumab–Paclitaxel for HER2+ cases, followed by anthracyclines. Surgery was performed 4– 6 weeks after PCRT. Pathologic response was graded using the Miller–Payne system. Toxicities were assessed per CTCAE v5.0. Survival outcomes were analyzed using Kaplan–Meier estimates. Results: Between September 2018 and August 2022, 62 patients were enrolled (median age 53 years). Tumor subtypes were 28 TN (45%) and 34 HER2+ (55%). Breast-conserving surgery was achieved in 68% of cases. Pathologic complete response (pCR, Grade 5) was obtained in 60% overall—70% in TN and 52% in HER2+ patients. A total of 43% of patients experienced acute G2, 26% G3, and 13.7% G4 cytopenia. The 7% experienced transient decline in left ventricular ejection fraction, all reversible. Two patients (3%) died before surgery, one due to a sepsis following chemotherapy-induced pancytopenia and second due to unrelated to treatment causes. With a median follow-up of 60.7 months, no grade ≥ 3 late toxicity was observed. The 5-year locoregional recurrence-free survival was 100%, disease-free survival 95%, distant metastasis-free survival 95%, and overall survival 95%. A total of 2 patients (3%) developed an independent contralateral primary breast tumor during the follow- up; both cases were treated according to standard protocols, and both remain free of disease to date. However, a total of 3 patients experienced distant disease recurrence.Only one death was cancer- related. Cosmetic results were rated as excellent or good in all breast-conserving cases. Reconstruction- outcomes favored autologous over heterologous techniques (p = 0.003). No significant correlation was found between pCR and survival. Conclusion: Preoperative concurrent chemoradiotherapy combining hypofractionated VMAT and systemic therapy in HER2+ and TN breast cancer demonstrated excellent local control, favorable survival, and acceptable toxicity after five years. References: Ciervide, R.; Montero, A.; Garcia-Aranda et al Neoadjuvant Chemoradiation for Unfavourable Breast Cancer Patients: A Prospective Cohort Study.J Clin Trials 2019, 9:3; 2019.Ciervide, R.; Montero, A.; García- Rico, et al. Primary Chemoradiotherapy Treatment (PCRT) for HER2+ and Triple Negative Breast Cancer Patients: A Feasible Combination. Cancers (Basel).2022
Figure1: Comparison of the percentage changes of Δ (TCP)% and Δ (V95)% (AXB vs. AAA) regarding the PTV Conclusion: Both IMRT and VMAT are feasible alternatives for ultrahypofractionated breast radiotherapy. The AXB algorithm provides improved tumor dose estimation and may enhance the clinical accuracy of dose calculation compared to AAA. References: 1. Murray Brunt A, Haviland JS, Wheatley DA, Sydenham MA, Alhasso A, Bloomfield DJ, et al. Hypofractionated breast radiotherapy for 1 week versus 3 weeks (FAST-Forward): 5-year efficacy and late normal tissue effects results from a multicentre, non-inferiority, randomised, phase 3 trial. Lancet. 2020 May 23;395(10237):1613–26. Keywords: Ultrahypofractionation, dosimetry, Radiobiology Five-Year Outcomes of Preoperative Concurrent Chemoradiotherapy in HER2-Positive and Triple- Negative Breast Cancer Raquel Ciervide, Angel Montero, Mariola García- Aranda, Beatriz Alvarez, Jeannette Valero, Rosa Alonso, Xin Chen-Zhao, Mercedes Lopez, Ovidio Hernando, Emilio Sanchez, Daniel Zucca, Juan García Ruiz-Zorrilla, Miguel Angel De la Casa, Ana Martinez, Daniel Martin, Lydia Perez, Bruno Zambrana, Raquel Sanchez, Pedro Fernandez-Leton, Carmen Rubio Radiation Oncology, HM Sanchinarro, Hospitales, Madrid, Spain Purpose/Objective: Concurrent chemoradiotherapy (PCRT) is well- established in several solid tumors, but its role in breast cancer remains under investigation. We report five-year clinical outcomes, tolerance, and survival after preoperative concurrent chemoradiotherapy in patients with HER2-positive (HER2+) and triple- negative (TN) breast cancer. Material/Methods: A prospective pilot-study including 62 patients with non-metastatic HER2+ or TN breast carcinoma was initiated in 2018. All patients received concurrent Digital Poster Highlight 4801
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