Prognostic Factors Influencing Survival and Oncological Outcome in Patients with Parosteal Osteosarcoma

This study aimed to evaluate the significance of radiological (magnetic resonance imaging [MRI]) findings, surgical, and previous interventions on prognosis with oncological and functional outcome in patients with parosteal osteosarcoma (POS). Twenty-seven patients (8 male/19 female) who were operated with the diagnosis of primary POS in our institution were retrospectively reviewed. The epidemiological data, biopsy method, misdiagnosis/improper interventions, and delay in diagnosis were noted. The lesions' maximum circumferential extension, maximum longitudinal extension, intramedullary involvement, and neurovascular extensions in MRI sections were evaluated, and the resection type (segmental intraarticular/segmental intercalary/hemicortical), reconstruction type (biologic/non-biologic), and surgical margins were noted. Functional and oncological results at the last follow-up were assessed. The mean age was 31.6 (12-73) years, and mean follow-up was 80.8 (24-270) months. Intramedullary involvement percentage was related with maximum circumferential extension percentage and maximum longitudinal extension. (p = 0.006, p = 0.005) The intramedullary involvement ratio of ≤ 10% suggested no recurrence or metastasis. The neurovascular encasement was related to metastatic disease, deep infections, and complication related surgeries (p = 0.017, p = 0.002, p = 0.005). The most common resection type was segmental intraarticular resection (63%). The maximum circumferential extension percentage, the maximum longitudinal extension of the lesion, intramedullary involvement percentage, and neurovascular encasement had lower MSTS scores (p = 0.003, p = 0.028, p = 0.038, p = 0.022). The mean MSTS score was 81.1% (60-100%). The 5-year overall survival was 96.3%, local recurrence-free survival was 77.2%, and metastasis-free survival was 69.4%. The lesions' extent of intramedullary involvement, neurovascular bundle proximity, and maximum periosteal circumferential extension on MRI should be considered when planning the surgery.