Retroperitoneal soft tissue sarcoma: low-dose neoadjuvant radiation therapy followed by surgery with or without intraoperative radiotherapy and adjuvant radiation therapy.

BACKGROUND: We describe the clinical history, outcome, and toxicity of five patients with high-grade retroperitoneal soft tissue sarcoma (RSTS) who were treated with neoadjuvant low-dose radiotherapy (RT) followed by resection with or without intraoperative radiotherapy (IORT), followed by adjuvant RT. We aim to provide additional evidence for the various treatment options that exist for this rare tumor entity. METHODS: Most patients presented with mild abdominal symptoms. Diagnosis was confirmed by biopsy. Additional imaging was done by sonography, magnetic resonance imaging (MRI), and/or positron emission tomography (PET)/computed tomography (CT). All patients were treated with neoadjuvant RT of 19.8 Gy in 1.8-Gy fractions followed by resection and postoperative RT up to 45 Gy with a median interval between resection and start of postoperative RT of 5 weeks. Two patients received additional IORT. Median follow-up was 61 months. RESULTS: One patient developed a local recurrence that was diagnosed 30 months after the start of the first therapy. He was treated with a salvage resection and had no evidence of disease at the last follow-up. Another patient developed a right-sided RSTS on the contralateral side from the primary radiation field with pelvic bone infiltration 56 months after the start of RT. He was treated again by RT and resection and was without evidence of disease at last follow-up. Radiotherapy was well tolerated without major toxicity. CONCLUSION: The treatment of RSTS by low-dose neoadjuvant RT, resection with IORT and adjuvant RT seems to be a feasible and effective treatment approach. Further studies comparing neoadjuvant with adjuvant RT are necessary to find the best treatment option.