Comparing Ultra-hypofractionated Proton versus Photon Therapy in Extremity Soft Tissue Sarcoma

Area of Science:

• Radiation Oncology
• Medical Physics
• Surgical Oncology

Background:

• Ultra-hypofractionated preoperative photon therapy (5 fractions) shows feasibility and efficacy for soft tissue sarcoma (STS).
• Neoadjuvant radiation therapy (RT) is used for adult extremity STS.
• Scanning beam proton therapy (PT) is a modern RT technique.

Purpose of the Study:

• To compare the dosimetric benefits of scanning beam proton therapy (PT) versus conventional photon radiation therapy (RT).
• To evaluate PT and RT for neoadjuvant treatment of adult extremity STS.

Main Methods:

• Retrospective analysis of 11 adult STS patients' existing proton and photon plans.
• Delineation of volumes and dose reporting per ICRU reports 50, 62, and 78.
• Comparison of target coverage, organ at risk (OAR) constraints, and integral dose between PT and intensity-modulated RT (IMRT) using Student's t-test.

Main Results:

• Proton therapy achieved 99% clinical target volume (CTV) coverage, meeting OAR constraints.
• Significantly lower mean doses to the femur, femoral head, and proximal joint observed with PT compared to IMRT (P < .05).
• PT demonstrated significantly reduced integral dose, improved conformity, and better heterogeneity indices compared to photon plans.

Conclusions:

• Proton therapy maintained target coverage while significantly reducing integral and mean doses to proximal organs at risk compared to conventional RT.
• Further prospective studies are needed to validate these dosimetric findings and the potential clinical benefits of PT in adult STS management.