Custom Mega Prosthesis in Metachronous Osteosarcoma

Background: The objective of the current study was to determine the incidence, clinical and pathologic characteristics, and outcome of patients with conventional osteosarcoma who developed metachronous tumours and treated by limb salvage surgery with Custom Mega Prosthesis. Methods: Among 1198 osteosarcoma patients who were treated with limb salvage surgery and implantation of custom mega prosthesis, 6 patients were found to have metachronous lesions. The absence of pulmonary metastases was confirmed by chest radiographs and computed tomography while radionuclide bone scan and biopsy were used to confirm the absence of skeletal metastases. The patients were treated by limb salvage surgery with custom mega prosthesis for the metachronous tumour and functional outcome was evaluated by MSTS scores. Results: Index primary tumours involved the femur (n=3) and the tibia (n=3) and were treated with limb salvage surgery using endoprosthetic reconstruction. Single metachronous tumours developed in the all of these patients with the interval between identification of the primary tumour to development of the metachronous tumours varying from 18 months to 41 months. All metachronous tumours were treated with neoadjuvant chemotherapy and limb salvage surgery. We obtained excellent functional outcome for primary tumours and good functional outcome for metachronous tumours. Two patients succumbed to disease due to pulmonary and cerebral metastasis during follow-up. Conclusions: With advances in survival rate in the multidrug chemotherapy era in the post tumoursresection period, advanced diagnostic modalities help in diagnosing metachronous osteosarcoma. It should be recognized as important sequelae in long-term survivors. Meticulous follow-up is required to permit early detection and successful therapeutic intervention. Limb salvage surgery has provided consistent good results in metachronous osteosarcoma patients.