Anatomic changes in head and neck intensity-modulated proton therapy: Comparison between robust optimization and...

Area of Science:

• Medical Physics
• Radiation Oncology
• Medical Imaging

Background:

• Head and neck intensity-modulated proton therapy (IMPT) quality is sensitive to setup variations and anatomical changes.
• Robustness strategies, including a priori robust optimization and online adaptation, aim to mitigate these effects.

Purpose of the Study:

• To compare the efficacy of classical robust optimization (cRO), anatomical robust optimization (aRO), and daily online adaptation (OA) for head and neck IMPT.
• To evaluate treatment plan quality in terms of target coverage and organ-at-risk (OAR) dose.

Main Methods:

• Three IMPT plans were created for 10 head and neck squamous cell carcinoma (HNSCC) patients: cRO, aRO (including initial daily CBCTs), and OA (re-optimized daily).
• Cone-beam computed tomography (CBCT) was used for daily evaluation.

Main Results:

• Online adaptation (OA) achieved clinical target volume (CTV) coverage in all 10 patients, surpassing aRO (8 patients) and cRO (4 patients).
• OA significantly reduced integral dose to healthy tissues and provided equivalent or superior target coverage compared to robust methods.
• aRO showed minimal increase in OAR dose over cRO, but with a higher integral dose.

Conclusions:

• Daily online adaptation using spot intensity re-optimization is a superior strategy for head and neck IMPT.
• OA achieves better target coverage and lower OAR dose than traditional robust optimization techniques.