Normal tissue outlining guidelines development for soft tissue sarcoma of the extremities.

Area of Science:

• Radiation Oncology
• Medical Imaging
• Surgical Oncology

Background:

• Radiotherapy (RT) for soft tissue sarcoma of the extremities (STSE) requires precise planning to maximize tumor coverage and minimize dose to normal tissues (NT).
• Current NT outlining practices can lead to variability, potentially impacting treatment outcomes and toxicity.

Purpose of the Study:

• To develop and evaluate novel lower extremity NT outlining guidelines and an atlas for STSE radiotherapy planning.
• To assess the usability and applicability of these guidelines in reducing RT toxicity.

Main Methods:

• Development of NT outlining guidelines and an atlas.
• Two STSE cases were used, with reference volumes outlined by a Therapeutic Radiographer/Radiation Therapist (RTT) and reviewed by a Radiation Oncologist (RO).
• Multiple observers (RTTs and ROs) outlined NTs using the guidelines, and interobserver variability was assessed using Dice coefficient (DICE), Maximum Hausdorff distance (maxHD), and mean surface distance (MSD).

Main Results:

• Good agreement and reproducibility were observed for muscle compartments, joints, and bony structures (femur, femoral head/neck).
• Moderate agreement was found for neurovascular bundles, with poor agreement specifically for the deep thigh neurovascular bundle.
• Consistent scores were achieved between RTTs and ROs, indicating multi-professional reproducibility.

Conclusions:

• The developed NT outlining guidance for STSE is reproducible across observers and within a multi-professional setting.
• The guidelines show potential for improving RT planning consistency and may help reduce RT toxicity.
• Areas for refinement, particularly for the deep thigh neurovascular bundle, have been identified.