Background: Retroperitoneal sarcomas (RPS), such as pleomorphic leiomyosarcoma, often invade or displace vital organs in the abdominal cavity and exhibit an aggressive clinical course. Complete surgical resection of the tumor and preoperative radiotherapy and chemotherapies can be used for non-metastatic RPS. However, in case of huge retroperitoneal sarcoma fully occupying the abdominal cavity, surgical resection tends to be insufficient, resulting in poor outcomes. This report describes a case of rapidly progressive retroperitoneal pleomorphic leiomyosarcoma that was favorably controlled by debulking surgery followed by combination chemotherapy and radiotherapy. Case presentation. A 65-year-old Japanese woman developed abdominal discomfort due to a huge retroperitoneal tumor fully occupying the abdominal cavity. The immunohistochemical diagnosis was pleomorphic leiomyosarcoma with high-grade malignancy and aggressive proliferative features. Debulking surgery could be performed, but the small residual tumor had rapidly grown to an approximately 22 cm in length on the major axis within 38 days after the operation. The patient's general condition progressively declined. Combination chemotherapy, consisting of doxorubicin and ifosfamide, was successfully administered for six cycles while maintaining dose intensity. The best objective response was a partial response, and the chemotherapy was well tolerated. Approximately 50 Gy of radiotherapy was delivered to the remaining tumor. This multimodal strategy resulted in progression-free survival for more than 17 months and achieved sustained symptomatic relief. Conclusions: Multimodal therapy with debulking surgery, combination chemotherapy and radiotherapy controlled a rapidly progressive retroperitoneal pleomorphic leiomyosarcoma. Maintaining dose intensity of the chemotherapy and radiotherapy might contribute to overall tumor control.
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