ESTRO 2025 - Abstract Book

S501

Clinical - Breast

ESTRO 2025

Material/Methods: We conducted a retrospective analysis of node-positive BC patients treated with adjuvant RT administered following a conventional fractionation schedule using a 3D-conformal technique to the chest wall or breast and only the IV axillary level. Patients who received breast-targeted RT underwent also a boost of 10 Gy in 5 fractions. The primary endpoint of the study was disease free survival (DFS). Secondary endpoints included loco-regional control (LRC), and Overall Survival (OS). Toxicity was documented according to the Radiation Therapy Oncology Group (RTOG) criteria. Univariate and multivariate Cox proportional-hazard regressions were conducted to identify factors influencing outcomes. Results: The inclusion timeframe covered January 2009 to July 2019. A total cohort of 343 patients was analyzed. The median lesion diameter was 23 mm (range 5–90) and the median number of positive lymph nodes was 7 (range 1–28), with a median lymph node ratio of 41.7% (range: 4.8–100%). Disease recurrence occurred in 100 (29.2%) patients, with a median onset time of 70 months (range: 1–173). The 5- and 10-year Kaplan-Meyer curves for DFS were 81.4% (95% CI: 79.3%–83.5%) and 60.9% (95% CI: 57.6%–64.5%), respectively. Loco-regional recurrence occurred in 39 (11.4%) patients, with a median control duration of 74 months (range 5–173). A total of 98 (28.6%) deaths were recorded, with a median OS of 76 months (range: 6–173). The figure depicts Kaplan-meyer curves for DFS, LRC and OS. Multivariate Cox analysis confirmed that lymph node ratio (HR = 9.76, 95% CI: 3.12–30.53, p = 0.0001), Luminal B subtype (HR = 2.03, 95% CI: 1.26–3.29, p = 0.004), and triple-negative subtype (HR = 2.70, 95% CI: 1.22–5.99, p = 0.01) were significant predictors of poor DFS. Lymphedema in the ipsilateral arm was reported in 32 (9.3%) patients, primarily Grade 1 or 2.