Main Session
Sep
28
PQA 04 - Breast Cancer, Patient Reported Outcomes/QoL/Survivorship, Functional Radiation Medicine, Hematologic Malignancies, Palliative Care, and International/Global Oncology
2774 - Local Control in Metastatic Breast Cancer: Outcomes of Hypofractionated Radiotherapy and SBRT for Locoregional Oligoprogression During Systemic Therapy
Presenter(s)
Esengul Kocak, MD - MD Anderson Cancer Center, Houston, TX
M. Kirli Bolukbas1, M. Sahin1, M. Yilmaz2, and E. Kocak1; 1Health Sciences University Bakirkoy Dr. Sadi Konuk Training and Research Hospital, Department of Radiation Oncology, Istanbul, Turkey, 2Health Sciences University Bakirkoy Dr. Sadi Konuk Training and Research Hospital, Department of Medical Oncology, Istanbul, Turkey
Purpose/Objective(s):
Locoregional oligoprogression during systemic therapy remains a challenge in de-novo metastatic breast cancer. Without effective local treatment, progressive lesions may evolve into clinically significant morbidity such as pain, ulceration and bleeding, malodor or discharge, lymphedema, and occasionally neurologic complaints. We aimed to assess locoregional control, metabolic response, and survival outcomes of hypofractionated RT/SBRT for locoregional oligoprogression.Materials/Methods:
We retrospectively reviewed 24 patients diagnosed with de-novo metastatic breast cancer between 2018-2025 who developed locoregional oligoprogression during systemic therapy and received hypofractionated RT/SBRT to progressive sites between 2023-2025. All cases were assessed with positron emission tomography–computed tomography (PET-CT) before RT and during follow-up. Treatment was delivered using volumetric modulated arc therapy (VMAT) with image-guided radiotherapy (IGRT). The most frequently used dose-fractionation schedules were 25 Gy in 5 fractions to the whole breast ± level I axilla; for more limited target volumes, 30-35 Gy in 5 fractions or 40 Gy in 8 fractions were preferred. Survival analyses were performed using the Kaplan–Meier method.Results:
Median age was 50 years (35-80). Subtype distribution was Luminal A 9.1%, Luminal B 40.9%, HER2-positive 36.4%, and triple-negative 13.6%. Locoregional oligoprogression occurred at a median of 19 months (6-77) and involved the breast only (54.5%), breast plus axilla (36.4%), axilla only (4.5%), or an internal mammary node (4.5%). Median lesion SUV was 9.75 (2.4-18.0) and decreased to 4.5 (0.0-6.0) at 3 months and 1.6 (0.0-3.0) at 6 months post-RT. At 3 months, complete response (CR) and partial response (PR) rates were 59.1% and 40.9%. At 6 months, among 19 evaluable patients, CR was 84.2% and PR was 10.5%, with local progression in only one patient (5.3%). Out-of-field locoregional progression occurred in 31.8%, whereas in-field progression was 4.5%. Seven patients with out-of-field locoregional recurrence underwent salvage re-irradiation, achieving CR in 5 and PR in 2; at last follow-up, durable locoregional outcomes were CR 77.3%, PR 18.2%, and persistent progression 4.5%. Median progression-free survival (PFS) was 14.0 months, with a 1-year PFS of 63.4%. Median distant PFS was 20.0 months, with a 1-year distant PFS of 88.1%. Median follow-up was 12 months (4-33); 1-year overall survival (OS) was 93.8%. No grade 3-4 toxicity was observed. Systemic therapy was changed after RT in 8 patients (36.3%).Conclusion:
In patients with de-novo metastatic breast cancer receiving systemic therapy, hypofractionated RT/SBRT for locoregional oligoprogression achieved high locoregional control with minimal toxicity and a short treatment duration.