ESTRO 2025 - Abstract Book

S609

Clinical - Breast

ESTRO 2025

4051

Digital Poster Largest series of real-world outcomes of patients with nodal oligometastases from breast cancer (nOMBC) receiving contemporary treatment Rima Sanjay Pathak 1,2 , Ajay Thomas Alex 1,2 , Rajiv Sarin 1,2 , Tabassum Wadasadawala 1,2 , Revathy Krishnamurthy 1,2 , Ashwini Khandavalli 1 , Shalaka Joshi 3,4 , Sushmita Rath 5,6 , Sneha Shah 7,8 , Palak Popat 9,10 , Purvi Haria 9,10 , Shrikant Kale 11,12 1 Department of Radiation Oncology, Tata Memorial Centre, Mumbai, India. 2 Department of Radiation Oncology, Homi Bhabha National Institute, Mumbai, India. 3 Department of Surgical Oncology, Tata Memorial Centre, Mumbai, India. 4 Department of Surgical Oncology, Homi Bhabha National Institute, Mumbai, India. 5 Department of Medical Oncology, Tata Memorial Centre, Mumbai, India. 6 Department of Medical Oncology, Homi Bhabha National Institute, Mumbai, India. 7 Department of Nuclear Medicine, Tata Memorial Centre, Mumbai, India. 8 Department of Nuclear Medicine, Homi Bhabha National Institute, Mumbai, India. 9 Department of Radiology, Tata Memorial Centre, Mumbai, India. 10 Department of Radiology, Homi Bhabha National Institute, Mumbai, India. 11 Department of Medical Physics, Tata Memorial Centre, Mumbai, India. 12 Department of Medical Physics, Homi Bhabha National Institute, Mumbai, India Purpose/Objective: Literature is scarce in reporting the outcomes of nodal oligometastatic breast cancer (nOMBC) treated with curative intent. We report the patterns of practice and failure, and clinical outcomes, in these patients. Material/Methods: We included selective, consecutive and curatively treated 190 nOMBC patients with 236 nodal sites from an IEC approved ambispective registry (2016-2024). Curative-intent therapy included systemic chemotherapy+/- Targeted+/- hormonal therapy as indicated, surgery, and RT to locoregional+/- metastatic site. This cohort included patients with mediastinal (prevascular/ paratracheal/ epiphrenic/ cardiophrenic; 35.6%), cervical (20.8%), and contralateral nodal sites like the axillary(24.2%) internal mammary(10.6%) and supraclavicular(7.2%). Majority patients received oligometastases directed therapy (OMDT); radiotherapy (RT) alone (64.8%), surgery alone (24.6%) or RT+surgery (2.9%) whereas 16 patients (6.8%) received only systemic therapy (ST) only as per clinicians’ choice. RT doses were 40Gy/15 fraction equivalent (67.8%) or higher. Results: With the median age of 49 years, 36.8%, 16.8%, 18.4%, and 27.9% patients had hormone-receptor (HR) +ve /Her2-ve, HR+ve/Her2+ve, HR-ve/Her2+ve, and triple-negative breast cancer(TNBC) respectively. The median follow-up was 24.6 months (95%CI 21.4-27.8months). Except for 2, all patients received systemic therapy. Of the 236 sites, 8 (3.4%) had local metastatic site progression and all sites had received OMDT (3 treated with RT and 5 surgery). Survival outcomes are shown in Table 1 for the full cohort and by receptor status. Figure 1 shows that patients with HR+ve disease had significantly better 3-year disease-free survival (DFS) and overall survival (OS) compared to HR-ve disease (DFS 60.4% vs 26.3% and OS 86.5% vs 50.7%; Both p<0.001). Brain was the predominant site of subsequent metastases (46%) among those with HR-ve disease. Both DFS and OS for those with mediastinal nodes vs contralateral regional nodes and contralateral axillary nodes vs all other sites were statistically similar. Five out of 16 patients who did not receive any OMDT experienced subsequent distant metastases but none recurred at the local metastatic site and had similar DFS or OS as those who received OMDT. None of the patients experienced OMDT induced grade≥3 acute or late toxicities