Exploring the Need for Plan Adaptation in Robustly Optimised Head and Neck Intensity Modulated Proton Therapy: A...

Area of Science:

• Radiation Oncology
• Medical Physics
• Oncology

Background:

• Intensity-modulated proton therapy (IMPT) offers precise dose delivery for head and neck (HN) cancers.
• Adaptive proton therapy (APT) aims to account for anatomical changes during treatment.
• Early clinical experience with APT in HN cancer requires detailed dosimetric analysis.

Purpose of the Study:

• To evaluate the clinical feasibility and dosimetric outcomes of APT in HN cancer patients treated with IMPT.
• To identify factors driving the need for plan adaptation and their dosimetric impact.
• To explore strategies for mitigating treatment uncertainties and optimizing APT workflows.

Main Methods:

• Retrospective analysis of the first 25 locally advanced HN cancer patients treated with IMPT.
• Cone-beam CT (CBCT) used for treatment verification and triggering adaptive replanning.
• Dosimetric analysis of target coverage, OAR doses, and anatomical changes; evaluation of anatomical robust optimization (ARO).

Main Results:

• A 68% adaptation rate was observed, primarily due to weight loss and postoperative changes.
• Adaptations were mainly triggered by target coverage issues, occurring later in treatment.
• Patient-specific ARO and workflow refinements reduced adaptation frequency by 46% in a subsequent cohort.

Conclusions:

• CBCT-triggered adaptive IMPT is feasible for HN cancer but resource-intensive.
• Systematic dosimetric evaluation during implementation is crucial for anticipating uncertainties.
• Proactive replanning protocols and workflow optimization are essential for efficient APT resource allocation.