ESTRO 2024 - Abstract Book

S561

Clinical - Breast

ESTRO 2024

Results:

The cohort comprises 445 patients treated with SRT for 902 metastases. At initial breast cancer diagnosis, hormone receptor(HR)-positive and HER2-negative disease, HR-positive and HER2-positive disease, HR-negative and HER2 positive disease, as well as HR-negative and HER2-negative disease was present in 38% (168/445), 19% (85/445), 14% (61/445), as well as 16% (69/445) of the patients, respectively. At initial breast cancer diagnosis, 80% (357/445) of the patients were treated with curative intent. At the first course of MDT, median age was 58 years (IQR 49-67), median Karnofsky performance status was 80 (IQR 80-90), 90% (401/445) had a controlled primary tumor, 71% (318/445) had oligometastatic disease (≤ 5 metastases), 37% (163/445) had ablative therapy to all metastases, 64% (285/445) were treated for intracranial, and 36% (160/445) for extracranial lesions. Median follow-up was 15.4 months. In the overall cohort and at the first course of MDT, median PFS was 8.6 months (95%-confidence interval [CI] 7.3-10.2 months). Median PFS was shorter in patients with intracranial SRT compared to patients with extracranial SRT (7.2 months vs. 13.8 months; p < 0.0001) (Figure 1). Median OS for the overall cohort was 27 months (95%-CI 22.9-32.2 months). Median OS for patients with intracranial SRT was 18.1 months vs. 40.7 months for patients with extracranial SRT (p < 0.0001). Local recurrence at 12 months was 19.1% (95%-CI 14.2-23.9%) for patients with intracranial SRT vs. 5.8% (95%-CI 1.8-9.8%) for patients with extracranial SRT (p < 0.001) (Figure 2). Acute toxicity of CTCAEv5 ≥ Grade 3 was present in 1% of patients (6/445), including one potentially MDT -associated death. Late toxicity of CTCAEv5 ≥ Grade 3 was present in 2% of patients (8/445) .