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External validation of a three-variable Ewing sarcoma prognostic score and incremental value of the Glasgow
Burak Paçacı1, Gül Akın2, Adem Deligönül2
1Department of Medical Oncology, Marmara University Faculty of Medicine, Başıbüyük Yolu Sk. No: 9/1, Maltepe, 34854 Istanbul, Türkiye.
Objective:
To externally validate a three-variable Ewing sarcoma score and assess the incremental prognostic value of the Glasgow prognostic score (GPS) in adults.
Methods:
This retrospective cohort included 133 adults treated at 10 Turkish centers (2010-2026). The Ewing score used metastases, tumor diameter >5 cm, and leukocytes >11 000/mm3; GPS used C-reactive protein >10 mg/L and albumin <3.5 g/dl. Outcomes were overall (OS) and event-free survival (EFS). Discrimination was assessed using the concordance index and time-dependent area under the curve. Center-clustered Cox models included the Ewing score and ordinal GPS. Bootstrap uncertainty was estimated within centers.
Results:
During a median 81.1-month follow-up, 67 deaths and 82 EFS events occurred. Ewing score concordance indices were 0.668 (95% bootstrap confidence interval [CI]: 0.613-0.721) for OS and 0.688 (95% CI: 0.641-0.734) for EFS. High-risk patients had inferior outcomes, but low- and intermediate-risk groups were not separated. Each one-level increase in GPS was associated with shorter OS (hazard ratio [HR]: 2.67, 95% CI: 1.95-3.65) and EFS (HR: 2.31, 95% CI: 1.44-3.69). GPS increased the concordance index by 0.091 (95% bootstrap CI: 0.041-0.143) for OS and 0.070 (95% bootstrap CI: 0.027-0.115) for EFS. Its OS association was strongest within 24 months and attenuated thereafter.
Conclusions:
The Ewing score identified a high-risk population but incompletely separated lower-risk patients. GPS added independent prognostic information, but the extension requires external validation before clinical use.