Clinical characteristics and prognostic factors of malignant fibrous histiocytoma of bone: a SEER population-based study

BACKGROUND: Malignant fibrous histiocytoma of bone (MFH-B) is an extremely rare type of bone tumor. We aimed to analyze the clinical characteristics of MFH-B and establish nomograms that predict the prognosis of patients with MFH-B based on prognostic factors. METHODS: A total of 250 patients diagnosed with MFH-B were included from the Surveillance, Epidemiology, and End Results (SEER) database. Kaplan-Meier curves and log-rank tests were conducted. Potential prognostic factors were identified using univariate and multivariate Cox regression analysis. Nomograms that predict 3- and 5-year overall survival (OS) and cancer-specific survival (CSS) were further developed and internally validated. RESULTS: The multivariate analysis suggested that OS of patients was associated with age ≥57 years [hazard ratio (HR), 1.916; 95% confidence interval (CI), 1.329–2.761; P<0.001], pelvic bones (HR, 1.742; 95% CI, 1.024–2.961; P=0.040) and other tumor sites (HR, 2.498; 95% CI, 1.515–4.120; P<0.001), Grade III/IV (HR, 1.750; 95% CI, 1.002–3.056; P=0.049), distant tumor stage (HR, 2.100; 95% CI, 1.351–3.263; P=0.001), tumor size ≥66 mm (HR, 2.629; 95% CI, 1.747–3.959; P<0.001) and no surgery (HR, 2.134; 95% CI, 1.380–3.300; P=0.001). We then developed nomograms based on the prognostic factors. The concordance index (C-index) of nomograms for OS and CSS were 0.74 (95% CI, 0.70–0.77) and 0.74 (95% CI, 0.70–0.78). Calibration plots suggested optimal concordance between the predictive outcomes of nomograms with the actual survival. CONCLUSIONS: This is the first sizable study that analyzed clinical characteristics and prognostic factors of MFH-B. The nomograms we established for MFH-B were effective tools to predict prognosis of individual patients. These tools can also help doctors identify mortality risk.