Preoperative stereotactic ablative radiotherapy enabling limb-sparing resection of biphasic synovial sarcoma: a case report

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Background Synovial sarcoma is a rare and aggressive subtype of soft tissue sarcoma that predominantly affects adolescents and young adults and poses significant therapeutic challenges when tumors are large or located near critical neurovascular structures. While surgery combined with radiotherapy represents the standard approach for local control, the optimal dose, fractionation, and timing of preoperative radiotherapy remain under investigation, particularly with the increasing use of hypofractionated and stereotactic techniques. Case presentation We report the case of a 19-year-old female with a large biphasic synovial sarcoma of the proximal lower limb. Induction chemotherapy with doxorubicin and ifosfamide resulted in volumetric tumor progression with only minimal metabolic response on 18 F-FDG PET-CT, indicating inadequate local disease control. A salvage neoadjuvant strategy using preoperative stereotactic ablative radiotherapy (SABR) was therefore adopted. The patient received 35 Gy in five fractions, followed by limb-sparing surgical resection 58 days later. Histopathological analysis demonstrated extensive treatment-related changes, with near-complete tumor necrosis and approximately 5% residual viable tumor, and all surgical margins were negative. At approximately 4.5 years of post-surgical follow-up, the patient remains free of local recurrence and distant metastasis, with preserved limb function and no severe acute or late radiation-related toxicity. Conclusions This case highlights the potential role of intermediate dose-escalated preoperative SABR as a salvage neoadjuvant strategy in biphasic synovial sarcoma refractory to chemotherapy, supporting its consideration within individualized multimodal treatment planning for selected high-risk soft tissue sarcomas.