S223
Clinical - Breast
ESTRO 2026
residual, initially suspect ALN (rALN) in planning CT can be challenging after surgery +/- neoadjuvant chemotherapy (NACT). In this study, we systematically compare pre- and postoperative axillary assessments to investigate the location and frequency of rALN metastases and the oncologic outcome in those patients. Material/Methods: We screened 1542 cases for patients with nodal- positive breast cancer with preoperative contrast- enhanced staging CT undergoing RT after axillary lymph node dissection (ALND) and included 152 patients. Based on initial staging CT and postoperative planning CT images, three radiologists specialized in breast cancer imaging assessed rALN in the planning CT (irrespectively whether it still fulfilled malignancy criteria). For patients with rALN, oncologic follow-up was assessed. Results: ALND mostly comprised level I-II and was performed in 6 hospitals by >39 different surgeons. In the included high-risk patient collective, 47.2% had rALN after ALND. Most rALN were located in level I.The median number of initial ALN metastases was 6 (1-33) and after resection of a median of 11 (4-35) a median of 2 rALN (1-15) were remaining. While the presence of rALN did not correlate with the number of resected ALN, ≥ 4 initial ALN metastases were a strong predictor of both additional level I/II and level III/IV metastases (Figure 1). All patients with rALN received RT of the breast or chest wall with a median of 50.4 Gy in 28 fractions. 98.6% received RT of level III-IV, 94.4% of level II, 61.1% of level I, and 93.1% of the internal mammary region (IMN). 33.3% received a boost to rALN/IMN. Patients with rALN without intentional irradiation of level I/II respectively received a median mean dose of 49.9/51.1 Gy and a mean V85% of 69.5%/79.2% of the prescribed dose in level I and II.After a median follow up of 28.5 months (7-85), only one recurrence occurred in the axilla (level I). N=12 experienced distant metastases.
Conclusion: Successful harmonization of hyperthermia treatment protocols was achieved across the three Dutch hyperthermia centers, establishing standardized treatment delivery, temperature monitoring, and data registration procedures. This standardization is essential for valid multicenter comparison of treatment outcomes and will contribute to establishing evidence-based standards of care for patients with locoregional recurrent breast cancer requiring postoperative re-irradiation with or without hyperthermia. The harmonized protocols have been implemented not only for the RT-HYPE study participants but for all patients receiving hyperthermia treatment at these centers. References: Buchholz et al, Gallagher et al, Bakker et al, Overgaard et al Keywords: harmonization hyperthermia recurrent Digital Poster 868 Predictors of residual axillary lymph nodes after axillary lymph node dissection and clinical outcomes after axillary radiotherapy Sophie T. Behzadi 1 , Thomas Huber 2 , Nicolas Lenhart 2 , Antonia Wiedemann 2 , Sophia Kiesl 1 , Jana Nano 1 , Sophie Maier 1 , Luisa Allwohn 1 , Rebecca Moser 1 , Georg P. Schmidt 3 , Evelyn Klein 3 , Marion Kiechle 3 , Stephanie E. Combs 1,4 , Kai J. Borm 1 1 Radiation Oncology, Technical University Munich, Munich, Germany. 2 Radiology, Technical University Munich, Munich, Germany. 3 Gynecology, Technical University Munich, Munich, Germany. 4 Radiation Sciences, Helmholtz Zentrum Munich, Munich, Germany Purpose/Objective: In breast cancer, radiotherapy (RT) of the dissected axilla is only recommended in case of residual axillary lymph node (ALN) metastases. However, detection of
Conclusion: Initial number of suspect ALN ( ≥ 4) is associated with a higher risk of rALN metastases. In our collective with high dose coverage to the dissected axilla, we observed excellent regional control despite rALN metastases. This potentially supports the concept in
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