Prognostic significance of the ratio of surgically resected to radiologically detected lung nodules in patients with metastatic osteosarcoma

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.