The factors that affect the prognosis of patients' metastatic osteosarcoma are still poorly understood. In this study, we investigated a new prognostic factor, the ratio of surgically resected to radiologically detected osteosarcoma lung nodules (SR/RD), which may have predictive value.
Patients and methods: Data from patients with metastatic osteosarcoma who underwent metastasectomy between January 2009 and December 2020, in a single center, were reviewed. The relationships between survival and the SR/RD ratio, timing of lung metastases, number of nodules, laterality, and presence of tumor necrosis at first metastasectomy were investigated.
Results: Among the 125 metastatic osteosarcoma patients, 80 patients had an SR/RD ratio ≤1. The median duration of follow-up was 72 months, ranging from 6 to 118 months. The five-year overall survival (OS) and postmetastasectomy event-free survival (EFS) for all patients were 36.5% and 18.1%, respectively. The five-year OS of patients with a low SR/RD ratio was 49.6% and that of patients with a high SR/RD ratio was 11.8 (P = 0.001). The two-year postmetastasectomy EFS rates of the high and low ratio groups were 24.1% and 9.4%, respectively (P = 0.001). The SR/RD ratio, number of nodules, and tumor necrosis had significant effects on OS and postmetastasectomy EFS in univariate analysis. A Cox proportional hazard model demonstrated that tumor necrosis and an SR/RD ratio >1 were associated with OS (HR = 1.8 and 2.01) and postmetastasectomy EFS (HR = 1,69 and 1.97).
Conclusions: A high SR/RD ratio of greater than 1 and poor tumor necrosis were significantly associated with poor survival among patients with metastatic osteosarcoma who had lung metastasectomy. The high SR/RD ratio may be a surrogate outcome for incomplete metastatic tumor resection.
Keywords: Metastatic; Osteosarcoma; Prognosis; Thoracotomy.
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