Prospective Evaluation of Dynamic Serum ProGRP for Treatment Response Monitoring in Ewing Sarcoma

Patients with newly diagnosed, histologically confirmed Ewing sarcoma who are scheduled to initiate first-line systemic treatment at Peking University People's Hospital will be prospectively enrolled. Treatment selection, including chemotherapy, surgery, and radiotherapy, will be determined by the treating physicians according to routine clinical practice and will not be assigned by the study protocol.

Peripheral blood samples will be collected before the initiation of chemotherapy (T0), after the second or third cycle of neoadjuvant chemotherapy and before the next cycle (T1), after completion of planned neoadjuvant chemotherapy and before definitive local treatment (T2), and at the first routine follow-up visit after surgery or radiotherapy (T3). If longitudinal surveillance is included in the final protocol, additional samples will be collected during routine follow-up.

Serum ProGRP will be measured using an electrochemiluminescence immunoassay. Radiographic response will be assessed according to RECIST version 1.1 by two independent radiologists blinded to the ProGRP results. Disagreements will be resolved by a third reviewer.

The primary analysis will evaluate the correlation between the percentage change in serum ProGRP from T0 to T2 and the percentage change in the sum of diameters of RECIST target lesions over the same period. Secondary analyses will evaluate early prediction of objective response, longitudinal ProGRP patterns, and associations with event-free survival.

Inclusion criteria

• 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.
• At least one evaluable lesion on baseline imaging; at least one measurable lesion according to RECIST version 1.1 is required for the primary outcome analysis.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.
• Estimated life expectancy greater than 3 months.
• Written informed consent provided by the participant or the participant's legally authorized representative.

Exclusion criteria

• 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.
• Clinically significant bleeding or a clear bleeding tendency within 3 months before enrollment.
• Severe renal impairment, defined as an estimated glomerular filtration rate (eGFR) below 30 mL/min/1.73 m².
• Pregnancy or breastfeeding.
• Any condition that, in the investigator's judgment, may compromise participant safety, interfere with study assessments, or prevent compliance with the protocol.