S1060
Clinical – Sarcoma, skin cancer, malignant melanoma
ESTRO 2026
dose was 81%. Median follow-up was 18 months. Five patients (10%) experienced local failure. Median local PFS was 17.7 months. Twenty-nine patients experienced distant progression. Median PFS was 16.7 months. Median OS was 19.8 months. The highest grade of acute toxicity experienced by patients was 27% with grade 1, 17% with grade 2, and 4% with grade 3. The highest grade of late toxicity experienced by patients was 12% with grade 1, 14% with grade 2, 29% with grade 3, 0% with grade 4, and 2% with grade 5. Grade 3 late toxicity was most commonly lymphedema or fibrosis. Conclusion: In this prospective trial of HFRT for intact STS, we report low rates of acute grade 3 or greater toxicity, high rates of LC, and moderate rates of late grade 3 or greater toxicity. Distant progression is common in this patient population, which limits the benefit of LC. Keywords: Hypofractionation, dose escalation, MRI- guidance
Proffered Paper 5182
Results of a prospective, single-institution, phase II trial of hypofractionated radiation therapy for inoperable soft tissue sarcoma Bradley Eckelmann 1 , Grace Blitzer 1 , Marissa Ziolkowski 2 , Jennifer Smilowitz 1 , Marissa Weiss 1 , Sharon Weber 3 , Daniel Abbott 3 , Patrick Varley 3 , Heather Neuman 3 , James Maloney 4 , James Hinshaw 5 , Brett Morris 1 , Steven Howard 1 , Kristin Bradley 1 , Andrew Baschnagel 1 , Michael Bassetti 1 , David Hennessy 6 , Zachary Morris 1 1 Department of Human Oncology, University of Wisconsin, Madison, USA. 2 School of Medicine and Public Health, University of Wisconsin, Madison, USA. 3 Division of Surgical Oncology, University of Wisconsin, Madison, USA. 4 Division of Cardiothoracic Surgery, University of Wisconsin, Madison, USA. 5 Department of Radiology, University of Wisconsin, Madison, USA. 6 Department of Orthopedics and Rehabilitation, University of Wisconsin, Madison, USA Purpose/Objective: Radiation therapy (RT) can provide local tumor control (LC) for soft tissue sarcoma (STS) in both palliative and definitive settings. Conventionally fractionated RT (CRT) provides modest rates of LC for intact STS. To our knowledge, no prospective studies to date have evaluated the safety and efficacy of dose-escalated hypofractionated RT (HFRT) as treatment of intact STS. We hypothesized that dose-escalated HFRT for intact STS could achieve higher rates of LC than reported in trials of CRT. Material/Methods: An IRB-approved single institution prospective phase II clinical trial of dose-escalated HFRT as local control for STS was designed and completed planned accrual. Patients underwent HFRT utilizing either CT-guided radiation (24, 50%) or MRI-guided radiation treatments (24, 50%). Data on patient characteristics, RT dose and fractionation, LC, toxicity, and survival was collected. The primary endpoint was LC (stable, partial, or complete response according to RECIST) at two years after completion of RT. Secondary endpoints were acute and late toxicity, rates of complete response, five-year local tumor control, PFS and OS. Acute and late toxicity were graded on the CTCAE v5.0 scale during and after treatment. Results: Forty-eight patients were enrolled, 16 with non- metastatic localized disease and 32 with metastatic disease. The majority of patients (65%) had grade 3 disease. Median patient age was 64. Twenty-six men and 22 women were treated, with a median of one treated lesion per patient. Median RT dose was 54 Gy in six fractions. Median volume of treated disease was 356 mm3. Median PTV coverage by the prescribed
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