S237
Clinical - Breast
ESTRO 2026
Keywords: locoregional radiation therapy, NAC
Digital Poster 1298 Personalized fatigue trajectories during contemporary adjuvant breast radiotherapy: A prospective longitudinal study Efrat Gur 1 , Dana Elhadad 1 , Hagit Haraty 2 , Hadas Kugler 2 , Tomer Meirson 2 , Marina Mantzovsky 1 , Dror Limon 1 , Gal Markel 2 , Gali Jacobson 1 1 Radiotherapy, Beilinson medical center, Petah-Tikva, Israel. 2 Oncology, Beilinson medical center, Petah- Tikva, Israel Purpose/Objective: Radiation therapy is a cornerstone of breast cancer management in most cases. Fatigue is one of the most common and distressing treatment-related symptoms, affecting approximately 75-85% of breast cancer patients during adjuvant radiotherapy (RT). Despite its prevalence, the temporal dynamics and modifying factors of radiation-related fatigue remain incompletely understood.This prospective study aimed to characterize real-time fatigue trajectories throughout RT and to examine how prior systemic therapy influences fatigue patterns. Material/Methods: This study included 51 breast cancer patients who underwent adjuvant RT (15 fractions) and completed the FACIT-F questionnaire at three key timepoints: before RT (T0), mid-RT (T1), and 10–14 days post-RT (T2). Participants were stratified by prior systemic treatment exposure (neo-adjuvant or adjuvant) and systemic therapy-naive. Fatigue dynamics were assessed using the Trial Outcome Index (TOI), integrating fatigue, physical, and functional well-being domains, and evaluated with linear mixed-effects models adjusted for baseline characteristics and treatment group, including random intercepts to account for repeated measures. Results: Overall TOI scores declined across the treatment course (T0: 83.1; T1: 75.1; T2: 72.7). Patients with regional nodal irradiation demonstrated a statistically significant reduction in TOI score (p=0.03). Similarly, patients younger than 50 years showed a significant decrease in this index compared with those aged 50 years or older (p=0.01). Systemic therapy–naive patients exhibited the sharpest deterioration (T0 → T1: -13.9 p=0.001, T0 → T2: -19.1 P<0.001), while those previously treated with neoadjuvant therapy or adjuvant treatment maintained persistently low but stable scores (T0 → T2: 1.8 P=0.8). Emotional well-being and social score remained relatively stable across all groups and timepoints Conclusion:
Conclusion: De-escalating locoregional RT according to risk group after PST seems to be safe regarding 10-year LRR and LRR* rates. No significant differences in recurrences were seen between the risk groups. Moreover, TN patients showed only early LRR*, and hormone- negative patients had a higher LRR* rate than hormone-positive patients. References: 1. Mamounas EP, Bandos H, White JR, et al. Omitting
Regional Nodal Irradiation after Response to Neoadjuvant Chemotherapy. N Engl J Med. 2025;392(21):2113-2124.
doi:10.1056/NEJMoa2414859 2. de Wild SR, de Munck L, Simons JM, et al. De-escalation of radiotherapy after primary chemotherapy in cT1-2N1 breast cancer (RAPCHEM; BOOG 2010-03): 5-year follow-up results of a Dutch, prospective, registry study. Lancet Oncol. 2022;23(9):1201-1210. doi:10.1016/S1470- 2045(22)00482-X
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