This single-center prospective observational study aims to evaluate whether longitudinal changes in serum pro-gastrin-releasing peptide (ProGRP) reflect treatment response in patients with newly diagnosed Ewing sarcoma. Serum ProGRP levels will be measured before systemic treatment, during neoadjuvant chemotherapy, before local treatment, and after local treatment. Changes in ProGRP will be compared with radiographic tumor response assessed according to RECIST version 1.1. The study will also explore the ability of early ProGRP changes to predict objective radiographic response and the association between ProGRP patterns and event-free survival. ProGRP results obtained for research purposes will not be used to guide clinical treatment decisions.
Age 10 to 60 years.
Histologically confirmed Ewing sarcoma.
Newly diagnosed disease and scheduled to initiate first-line systemic therapy at Peking University People's Hospital.
No prior systemic chemotherapy for Ewing sarcoma and no prior radiotherapy to the primary tumor.
History of another malignant tumor within the previous 3 years, except for an adequately treated malignancy with a negligible risk of recurrence, as determined by the investigator.
New York Heart Association (NYHA) class III or IV heart failure.
Uncontrolled concomitant illness, including uncontrolled diabetes mellitus or an active infection.
Severe infection requiring intravenous antimicrobial treatment within 4 weeks before enrollment.
The study population will consist of patients aged 10 to 60 years with newly diagnosed, histologically confirmed Ewing sarcoma who are scheduled to initiate first-line systemic therapy at Peking University People's Hospital. Eligible participants must have at least one evaluable lesion on baseline imaging and must not have received prior systemic chemotherapy for Ewing sarcoma or radiotherapy to the primary tumor. Participants will receive chemotherapy and definitive local treatment, including surgery and/or radiotherapy, according to routine clinical practice. Treatment will not be assigned by the study protocol, and serum ProGRP results obtained for research purposes will not be used to guide clinical treatment decisions.
Cohort
Prospective
Not listed
Correlation Between the Change in Serum ProGRP and the Change in Tumor Size
The percentage change in serum ProGRP from baseline (T0) to the pre-local-treatment assessment (T2) will be calculated as \[(ProGRP at T2 - ProGRP at T0) / ProGRP at T0\] × 100%. The percentage change in tumor size will be calculated using the sum of diameters of RECIST 1.1 target lesions over the same period. The association between the two continuous variables will be quantified using Spearman's rank correlation coefficient.
Accuracy of Early Change in Serum ProGRP for Predicting Objective Radiographic Response
Receiver operating characteristic analysis will be used to evaluate whether the percentage change in serum ProGRP from T0 to T1 predicts objective radiographic response at T2. Objective response is defined as complete response or partial response according to RECIST version 1.1. The area under the receiver operating characteristic curve and its 95% confidence interval will be reported.
Objective Response Rate Before Definitive Local Treatment
Percentage of participants achieving complete response or partial response according to RECIST version 1.1 at the T2 assessment.
Longitudinal Change in Serum ProGRP
Serum ProGRP concentration in pg/mL and its percentage change from baseline will be summarized at T1, T2, and T3.
Event-free Survival
Event-free survival is defined as the time from initiation of first-line systemic treatment to the first occurrence of disease progression, local recurrence, a new metastatic lesion, or death from any cause. Participants without an event will be censored at the date of their last confirmed event-free assessment.
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