Recurrent Unresectable Retroperitoneal Liposarcoma Treated with Partially Ablative Body Radiotherapy: A Case Report

Purpose: To report the technical details and outcomes of a recurrent unresectable retroperitoneal liposarcoma treated with partially ablative body radiotherapy (PABR). Materials and Methods: A 70-year-old female patient with retroperitoneal dedifferentiated liposarcoma presented with multiple local recurrences after resection - one occurring four months after primary surgery and another occurring eight months after salvage surgery. At this latest recurrence, she experienced abdominal pain, vomiting and bleeding from her colostomy. Deemed unresectable and ineligible for chemotherapy, she was offered PABR. The prescribed radiotherapy dose was 20 Gy to the macroscopic tumor and 50 Gy to the tumor core, given via simultaneous integrated boost. This was delivered in five fractions performed every other day using image-guided volumetric modulated arc therapy. Results: The final treatment plan met dose constraints of nearby organs-at-risk – (the remaining kidney, bowels and spinal cord). Treatment was tolerated with one episode of grade 2 pain flare, which resolved with steroids. There were no grade >2 treatment-related adverse effects. Eight months post radiotherapy, the retroperitoneal mass decreased in size by 53%, as seen on re-evaluation whole abdominal computed tomography (CT) scan. There was no reported symptom recurrence and the patient was able to resume normal activities of daily living. Conclusion: This case report shows that PABR is technically feasible even in a low-middle-income setting. There was durable response with minimal toxicity at eight months follow-up, suggesting that it can be a useful modality to palliate bulky tumors. Prospective studies are warranted.