Does magnetic resonance imaging improve soft tissue sarcoma contouring for radiotherapy?

Area of Science:

• Oncology
• Radiotherapy
• Medical Imaging

Background:

• Soft tissue sarcomas (STS) are rare and diverse tumors.
• Radiotherapy is crucial for local control, but CT has poor soft tissue definition.
• Contour variation among oncologists impacts treatment outcomes.

Purpose of the Study:

• To compare soft tissue sarcoma tumor contouring between CT and MRI.
• To evaluate interobserver and intraobserver variation in contouring.
• To assess the impact of imaging modality on contour accuracy and consistency.

Main Methods:

• Eight STS patients' CT and MRI scans were contoured by four oncologists.
• Gross tumor volume was delineated using in-house software.
• Metrics including mean distance to agreement (DTA), DSC, and contour volume were analyzed.

Main Results:

• MRI resulted in significantly smaller tumor volumes (21.4 cm³ difference, p=0.008).
• No significant difference in mean DTA or DSC between CT and MRI.
• Standard deviation of DTA showed significant improvement with MRI (p=0.04), indicating reduced interobserver variation.

Conclusions:

• MRI leads to smaller tumor volume contours and reduced interobserver variation in STS radiotherapy planning.
• Improved contouring reliability with MRI may enhance quality assurance.
• Further experience with MRI may reduce inter-oncologist variation, improving local control and reducing toxicity.