2356 - Personalized Ultra-Fractionated Stereotactic Adaptive Radiotherapy (PULSAR) for Sarcoma Metastases
Presenter(s)
A. C. Merritt1, M. Kozak2, A. Callan3, A. Dann4, A. Jones5, S. Chandrasekaran5, D. Wang5, and K. A. Kumar2; 1University of Texas Southwestern Medical School, Dallas, TX, 2Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 3Department of Orthopaedic Surgery, University of Texas Southwestern Medical Center, Dallas, TX, 4Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX, 5Department of Internal Medicine, Division of Hematology/Oncology, UT Southwestern Medical Center, Dallas, TX
Purpose/Objective(s): PULSAR is a novel treatment that delivers high-dose pulses of radiation at extended intervals to allow treatment adaptation and optimize synergy with concurrent immuno- and other systemic therapies. Our institution has implemented PULSAR for patients with oligometastatic and oligoprogressive sarcomas in both pediatric and adult populations. Here, we report our initial clinical outcomes with the hypothesis that PULSAR provides excellent local tumor control with acceptable toxicities.
Materials/Methods: This IRB-approved retrospective study evaluated pediatric and adult patients with soft-tissue and bone sarcoma metastases treated with PULSAR at UT Southwestern from 2022–2025. We collected patient demographics, tumor & treatment characteristics, and clinical outcomes, including local tumor control (LC), progression-free survival (PFS), overall survival (OS), and toxicities. Kaplan-Meier analysis was used for survival outcomes.
Results: Among 34 irradiated metastatic sites in 14 patients (36% pediatric, 64% adult), metastases were most commonly lung/intrathoracic (71%), followed by bone (12%), soft tissue (12%), and abdominal/retroperitoneal sites (12%). Concurrent systemic therapy was administered in 93% of patients (13/14): chemotherapy (50%), immunotherapy (21%), and targeted therapy (21%). Systemic therapy integration was highly individualized. 3 patients switched regimens at PULSAR initiation, 6 continued their existing therapy throughout, 4 started a new systemic therapy concurrently with PULSAR, and 1 received PULSAR without any systemic therapy. Most patients (11/14) continued the same regimen following PULSAR. The most common dose was 8 Gy/pulse every 3 weeks × 5 (40 Gy cumulative). With a mean follow-up of 11 months (interquartile range 4-14 months), LC was 86% and 81% at 6- and 12-months, respectively. The majority of patients (57%) experienced no treatment-related toxicity. Of the 6 patients (43%) who did experience toxicity, radiation pneumonitis was the most common, occurring in 4/10 (40%) patients receiving thoracic radiation (all who had concurrent systemic therapy), though only one (10%) was Grade 3+.
Conclusion: In metastatic sarcomas, PULSAR provides excellent local control with limited toxicity despite high rates of concurrent systemic therapy. Its flexibility to accommodate individualized systemic therapy approaches is a key strength. Caution may be warranted when combining PULSAR with immunotherapy for lung metastases given the observed incidence of radiation pneumonitis, though severe toxicity was rare. These promising findings warrant further prospective study.