Dose response and local control using radiotherapy in non-metastatic Ewing sarcoma

Area of Science:

• Oncology
• Radiation Oncology
• Pediatric Oncology

Background:

• Ewing sarcoma (ES) is a rare bone cancer primarily affecting children and young adults.
• Effective management of localized ES requires optimizing local control to prevent recurrence.
• Identifying prognostic factors for radiotherapy outcomes is crucial for treatment planning.

Purpose of the Study:

• To identify prognostic factors influencing local control in non-metastatic Ewing sarcoma treated with radiotherapy.
• To evaluate the impact of radiation therapy (RT) dose on local control rates in localized ES.
• To establish optimal RT dose thresholds based on tumor size for improved outcomes.

Main Methods:

• Retrospective analysis of 40 patients with localized ES treated with primary site RT.
• Median RT dose administered was 55.8 Gy, with chemotherapy given to 85% of patients.
• Median follow-up was 12.3 years, with local control assessed using Kaplan-Meier analysis and log-rank tests.

Main Results:

• The 5- and 10-year local control rate was 78.2% overall.
• RT dose was the sole significant prognostic factor for local control on multivariate analysis.
• Higher RT doses (≥49 Gy for tumors ≤8 cm, ≥54 Gy for tumors >8 cm) were associated with significantly improved local control rates (P < 0.05).

Conclusions:

• Radiotherapy dose is a critical determinant of local control in Ewing sarcoma.
• Tailoring RT dose based on tumor size is essential for maximizing local control.
• Specific RT dose recommendations are provided for tumors ≤8 cm and >8 cm to improve patient outcomes.