Prevalence, Risk Factors, and Prognostic Factors of Primary Malignant Bone Neoplasms with Bone Metastasis at Initial Diagnosis: A Population-Based Study.

Background: Bone metastasis (BM) has been proven to be responsible for the poor prognosis of primary malignant bone neoplasms (PMBNs). We aimed to identify the prevalence, risk factors, and prognostic factors for PMBNs patients with BM based on the Surveillance, Epidemiology, and End Results (SEER) database.

Methods: 4,758 patients diagnosed with PMBNs from 2010 to 2018 were selected from the SEER database. All patients were divided into two groups: the BM group or the non-BM group. Pearson's chi-square test and Fisher's exact method were used to assess baseline characteristics, and logistic regression analysis was applied to assess risk factors. In addition, a nomogram was constructed based on the results of Cox regression analysis among 227 patients with BM. The good performance and clinical applicability of the nomogram were tested by the concordance index, operating characteristic curve, area under the curve, calibration curves, and decision curve analysis.

Results: 227 (4.8%) patients had metastasis to bone at diagnosis. Primary site outside the extremities (axial: odds ratio, OR = 1.770; others: OR = 1.951), Ewing sarcoma (OR = 2.845), larger tumor size (5-8 cm: OR = 3.403; >8 cm: OR = 5.562), tumor extension beyond the periosteum (OR = 2.477), and regional lymph node metastasis (OR = 2.900) were associated with a higher risk of BM at the initial diagnosis of PMBNs. Five independent prognostic factors were found in the survival analysis: pathological type (chondrosarcoma vs. osteosarcoma: hazard ratio, HR = 0.342; Ewing sarcoma vs. osteosarcoma: HR = 0.592; and chordoma vs. osteosarcoma: HR = 0.015), marital status (HR = 2.457), pulmonary metastasis (HR = 1.934), surgery at the primary site (HR = 0.164), and chemotherapy (HR = 0.084). A nomogram based on these prognostic factors could be a good predictor of cancer-specific survival.

Conclusions: We identified the prevalence, risk factors, and prognostic factors correlated with BM in PMBNs patients. The related nomogram could be a practical tool for therapeutic decision-making and individual counseling.