ONCOLOGICAL AND FUNCTIONAL OUTCOME USING EXTRACORPOREAL IRRADIATION IN LIMB-PRESERVING SURGERY IN THE MANAGEMENT OF BONE AND SOFT-TISSUE SARCOMA

Biological reconstruction with extracorporeal irradiation and reimplantation is an alternative to endoprosthetic reconstruction following osseous resection of extremity bone sarcomas and soft tissue sarcomas (STS). This method involves en bloc resection of the tumour, irradiation of the bone and re-implantation. Limb salvage surgery with autologous bone graft is reported to have better functional outcome due to its precise anatomical fit. This study reports the oncological and functional outcomes of patients who had extracorporeal irradiation (ECI) and reimplantation in our centre. ECI Technique: Following wide resection, the bone segment was wrapped in sterile plastic bags and towels and placed in a box surrounded by water equivalent materials. The box was then irradiated with parallel opposed fields using 10 megavolt (MV) photons to a dose of 50Gy in one fraction. The resected bone was then returned back to the operating room and re-implanted. We reported the demographic information and summary statistics of all patients undergoing this procedure at our institution. Four patients were treated with ECI and biological reconstruction from July 2021 to October 2023. Three patients were female and one was male. Three patients had high grade conventional osteosarcoma (age range 10 – 28), and one had a high grade myxofibrosarcoma with cortical involvement of the distal tibia (age 70). All patients had lower limb disease including proximal and distal femur and proximal and distal tibia. Three patients had metadiaphyseal resections and one patient had osteoarticular resection. Patients with high grade conventional osteosarcoma had pre-operative chemotherapy as per the Children's Oncology Group AOST0331 protocol and the patient with myxofibrosarcoma had pre-operative radiotherapy to the primary STS prior to resection. One patient with high grade osteosarcoma had surgery one month ago, and thus will be excluded from further analysis due to lack of follow up data. At a median follow up time of 19 months (range 17- 27), the remaining three patients are alive and free from distant metastatic disease. No patients developed local recurrence after ECI. One patient had union at the osteotomy site at three months but then required a subsequent bone grafting procedure due to a non-union which happened 17 months after the initial surgery. Another patient had union at the osteotomy site uneventually at 13 months. One patient's irradiated autograft developed an infection and had to be removed and was replaced with a PROSTALAC implant. Adjuvant Doxorubicin chemotherapy was given without any unforeseen delay post ECI for two patients, at 16 and 21 days after surgery. Neither patient developed any acute radiotherapy toxicities. All patients had good functional outcomes and able to walk unaided at last follow up. From our experience, ECI offers excellent long term local control and is a good alternative to using endoprosthesis in patients with primary bone tumour and STS with bone involvement. Doxorubicin chemotherapy can be safely given within 3 weeks after ECI with no added risk of radiotherapy complications. Non-union and infection of the implanted autograft are possible complications post ECI.