Use Of Microwave Thermal Ablation In Management Of Skip Metastases In Extremity Osteosarcomas

BACKGROUND: The objective of this study was to evaluate the efficiency and safety of microwave thermal ablation in the treatment of skip metastases in extremity osteosarcomas. Osteosarcoma of extremities with skip metastases has a poor prognosis, and thus, microwave thermal ablation presents an attractive minimally invasive option in this patient group. METHODS: A retrospective review included a cohort of 76 patients with extremity osteosarcoma in one institute, of which five cases (6.6%) showed skip metastases. Skip lesions located in proximal femur and primary sites were distal femur in all five patients. The authors treated skip lesions using microwave thermal ablation after primary tumors were removed at wide margins. Procedural efficacy and safety were determined with postoperative MSTS score and follow-ups of 12–62 months (median 22 months). RESULTS: The ablation time was five to nine minutes (mean seven minutes). Taking advantage of Microwave-induced hyperthermia, wide resections of distal femur and endoprosthesis reconstructions were performed instead of total femoral resection and replacement in four patients, and above-knee amputation was performed instead of hip disarticulation in one patient. The postoperative hip functions were intact and the mean lower extremity MSTS score was 26. Three patients died at 12–22 months after definitive surgery because of pulmonary metastases, and two patients remained disease-free at 44 and 62 months after surgery, respectively. No local recurrence either at sites of primary tumors or skip lesions was found at time of the latest follow up. CONCLUSION: Microwave thermal ablation is efficacious in treating skip metastases of osteosarcoma in extremities. The modality has promise for good local control of tumors, less invasive surgeries, and intact and satisfied lower extremity functions in these relatively poor prognosis patients. LEVEL OF EVIDENCE: Therapeutic Level III.