Ewing's Sarcoma in Adults: A Predictive Nomogram and Survival Analysis of a Cohort of 937 Patients.

BACKGROUND: Ewing sarcoma is a rare malignancy of bone and soft tissue that most commonly affects children, adolescents, and young adults. Although multimodal treatment has improved survival in localised disease, outcomes remain poorer in adults, particularly in those with metastatic disease, larger tumours, or anatomically complex primary sites. Current staging systems are useful for treatment allocation but do not fully capture individual prognostic variation. This study aimed to develop and internally validate a predictive nomogram for disease-specific survival in adult patients with Ewing sarcoma. METHODS: A retrospective population-based cohort study was performed using the SEER-17 database from 2000 to 2015. Adult patients aged 18 years or older with histologically confirmed primary Ewing sarcoma of bone or soft tissue were included. The primary outcome was disease-specific survival. Predictor variables included age, sex, tumour site, tumour size, metastatic status, surgery, radiotherapy, and chemotherapy. Multivariable Cox proportional hazards regression was used to identify independent prognostic factors and construct a nomogram estimating 1-, 3-, and 5-year disease-specific survival. Internal validation was performed using 150 bootstrap resamples, and clinical utility was assessed using decision curve analysis. RESULTS: A total of 937 adult patients were included. The mean age was 33.9 years, and 556 patients were male. Extraosseous disease was the most common primary site, followed by axial bone and appendicular bone disease. Metastatic disease was present in 294 patients. Multivariable analysis identified metastatic disease, increasing age, larger tumour size, and absence of surgery as independent adverse prognostic factors. The nomogram incorporated age, clinical stage, primary site group, tumour size, surgery, and chemotherapy to estimate 1-, 3-, and 5-year disease-specific survival. Internal validation demonstrated an optimism-corrected C-index of 0.688, with acceptable calibration across the three time points. Decision curve analysis suggested that the full nomogram provided greater clinical utility than stage alone across intermediate threshold probabilities. CONCLUSION: This study developed and internally validated a population-based prognostic nomogram for adult patients with Ewing sarcoma. The model demonstrated acceptable discrimination and calibration, and may support individualised risk assessment, prognostic communication, and clinical decision-making. External validation in independent cohorts, incorporating molecular and treatment-intensity data, is required to further improve clinical applicability.