Combined Wide Resection and Bioabsorbable Spacer Placement for High-Dose Postoperative Radiotherapy in Retroperitoneal Dedifferentiated Liposarcoma: Considerations Regarding Metallic Coil Artifacts

Background Dedifferentiated liposarcoma is a high-grade malignant tumor for which complete surgical resection is the only curative treatment. In the retroperitoneum, however, achieving negative surgical margins is often challenging. When margin-negative resection is unlikely, postoperative radiotherapy may be required, but dose escalation is frequently limited by the tolerance of surrounding organs. Bioabsorbable spacers have been introduced to physically separate radiosensitive organs from the target volume. We report a case of retroperitoneal dedifferentiated liposarcoma in which a bioabsorbable spacer was intentionally placed during the initial surgery to facilitate safe delivery of high-dose postoperative radiotherapy. Case presentation A 72-year-old man presented with a large retroperitoneal tumor involving the psoas major muscle and ureter, closely abutting the left common iliac artery and kidney. Biopsy confirmed dedifferentiated liposarcoma. Because a high risk of intraoperative bleeding was anticipated, selective preoperative transarterial embolization using metallic coils was performed. The patient subsequently underwent en bloc tumor resection. Given the anticipated difficulty in achieving negative margins adjacent to the iliac vessels, a polyglycolic-acid bioabsorbable spacer was deliberately placed during the same operation to create a separation of approximately 15–20 mm between the bowel and the high-risk target area. Pathological examination revealed microscopically positive margins. Although proton therapy was initially considered, severe imaging artifacts from the embolization coils were expected to cause clinically relevant dose perturbation. Therefore, postoperative photon intensity-modulated radiotherapy was administered to a total dose of 70.4 Gy in 32 fractions. At 24 months after treatment, the patient remained free from local or distant recurrence without radiation-induced gastrointestinal toxicity. Conclusions Planned intraoperative placement of a bioabsorbable spacer during tumor resection can enable safe delivery of high-dose postoperative radiotherapy in retroperitoneal dedifferentiated liposarcoma when negative margins are difficult to achieve. However, metallic embolization materials may limit radiotherapy options, underscoring the importance of early multidisciplinary planning.