S221
Clinical - Breast
ESTRO 2026
reducing unnecessary morbidity. However, radiotherapy (RT) planning computed tomography (CT) provides a final opportunity to reexamine the axilla. This study evaluated the frequency, characteristics, and clinical significance of incidentally detected lymph nodes ≥ 1 cm in postoperative breast cancer patients
on RT planning CT. Material/Methods:
Between 2021 and 2025, 32 postoperative breast cancer patients with at least one axillary lymph node either ≥ 1 cm in short-axis diameter or morphologically suspicious (loss of fatty hilum, cortical thickening, or irregular contour) on RT planning CT were retrospectively analyzed. All patients underwent targeted axillary ultrasonography (USG), and positron emission tomography–computed tomography (PET-CT) was performed when indicated. An experienced breast radiologist and radiation oncologists jointly reviewed all imaging findings. Data were analyzed using descriptive statistics and univariate analysis. Results: The median age was 51 years (34-80). Histologically, 81.3% had invasive ductal and 18.7% had invasive lobular carcinoma. Molecular subtypes were Luminal A and B in 71.9%, triple-negative in 25.0%, and HER2- positive in 3.1%. Fifteen patients (46.9%) received NACT. Based on pathological staging, 71.9% were stage 0–2A and 28.1% stage 2B–3. In the topographic distribution, incidental lymph nodes were detected at level 1 in 28 patients (87.5%), at level 2 in 3 patients (9.4%), and at level 3 in 1 patient (3.1%). The median long-axis and short-axis diameter was 14 mm (11-30 mm), 11 mm (5-15 mm), respectively. USG-guided fine- needle aspiration biopsy in 20 cases revealed malignancy in 11 (55.0%), suspicious findings in 1 (5.0%), and benign cytology in 8 (40.0%). PET-CT was performed in 9 patients (28.1%) with a median SUV of 5.0 (2.06–14.0). Additional surgery was performed in 12 patients, with nodal involvement confirmed in 11 (91.6%). Overall, residual malignancy was detected in 11 of the 32 patients (34.4%), significantly associated with age ≥ 65 years (p=0.037), higher nodal stage at presentation (N2-3, p=0.035), prior axillary dissection (p=0.023), and advanced pathological stage (2B-3, p=0.003).
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