Nomogram to Predict Overall and Cancer-Specific Survival in Patients with Synovial Sarcoma in the Extremities: A Population-Based Study.

Background: Synovial sarcoma is a rare disease, and synovial sarcoma that first appears in the extremities accounts for more than 80% of cases. We established two nomograms to predict the overall survival (OS) and cancer-specific survival (CSS) rates of patients with synovial sarcoma. Methods: A total of 227 patients diagnosed with synovial sarcoma in the extremities between 2010 and 2015 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Univariate and multivariate Cox analyses were performed to explore independent prognostic factors and to create two separate nomograms for OS and CSS. The C-index, the area under the curve (AUC), calibration curve, decision curve analysis (DCA), and Kaplan-Meier (KM) curve were used to evaluate the column line graphs and analyze prognostic factors. Results: Age, Stage M, and surgery were identified as independent prognostic factors for OS and CSS. The ROC curve showed good discriminative power for the nomogram. Calibration curves and DCA curves showed that the nomogram had a satisfactory ability to predict OS and CSS. The KM curve showed that chemotherapy alone did not affect patient survival. Conclusion: Age, Stage M, and surgery are variables that affect OS and CSS in patients with synovial sarcoma in the extremities. Two nomograms were established based on the above variables to provide patients with more accurate individual survival predictions and to help physicians make appropriate clinical decisions.