LAUSR

11524 Background: Extracorporeal irradiation is an effective and established method for limb salvage in the management of malignant bone tumours.We analyzed the oncological and functional outcomes of extracorporeal radiotherapy (ECRT) and reimplantation done for bone sarcomas. Methods: 67 patients (29 osteosarcoma, 27 Ewing’s sarcoma, 11 others; mean age 16 years) were treated with ECRT between 2010 and 2022. Femur was commonest bone (33) followed by tibia (11) and humerus (11). 48 had a metadiaphyseal while 19 had osteoarticular resections. A single dose of 50 Gy was delivered to the resected bone segments. The irradiated bones were reimplanted immediately as a biological graft. Construct was stabilized with long locking plates. Osteoarticular ECRT was coupled with joint replacement. Patients were treated with chemotherapy as per standard protocol. Functional outcome was assessed by Musculoskeletal Tumor Society (MSTS) scoring system. Results: The mean resected length of bone was 17 cm (9 to 26). All 67 patients were available at a mean follow-up of 66 months (22 to 166). The mean time to union for all osteotomy sites was 6 months (2 to 17): metaphyseal osteotomy sites united quicker than diaphyseal osteotomy sites (3.8 months (3 to 6) versus 9.5 months (4 to 17)). 2 deep infections necessitated removal of the ECRT segment. There were 2 local recurrences in soft-tissue needing amputation. 6 of the remaining 113 (5.3%) junctions remained ununited which needed additional bone grafting. 5/6 junctions united after bone grafting. 1 remained ununited needing cementation across the segment. At the time of final follow-up, 47 patients were free of disease, one was alive with disease and 19 had died of disease. The mean Musculoskeletal Tumor Society Score at the last follow-up was 26 (18 to 30). Conclusions: The radiated bone acts as a size-matched allograft and has very good union rates. The complication rates are very low. Extracorporeal irradiation is an oncologically safe and biological reconstruction technique for limb salvage in sarcomas and has good functional results. It should be recommended to all suitable patients.