Pathologic Complete Response to Neoadjuvant Radiation Therapy in a Primary Pancreaticoduodenal High-Grade Sarcoma.

High-grade intra-abdominal sarcomas are a rare soft tissue malignancy with a high propensity to present in a locally advanced fashion. The role of radiation therapy (RT) in the management of intra-abdominal sarcomas is relatively under-reported, in contrast to its use in retroperitoneal or extremity sarcomas. We thereby present a case of a 63-year-old female presenting with abdominal pain, gastrointestinal (GI) bleeding, and weight loss, found to have a large, high-grade intra-abdominal pancreaticoduodenal sarcoma. Given ongoing bleeding, absence of actionable mutations, and surgical risk, she was treated with neoadjuvant RT (50 Gray in 25 fractions) using image-guided volumetric-modulated arc therapy. The patient tolerated treatment well with rapid and significant tumor regression, allowing for subsequent pancreaticoduodenectomy. Pathology revealed a complete pathologic response (ypT0N0M0) with no residual viable tumor. At 2.5 years post-treatment, she remains disease-free. This case highlights the potential role of neoadjuvant RT in achieving local control and facilitating curative resection in patients with high-grade intra-abdominal sarcomas. While evidence is limited, especially for visceral intra-abdominal sites, this report supports further investigation into RT as a component of multimodal therapy in select cases.