Defining a Quantitative Threshold for Adaptive Re-planning using a Percentile-based Scoring System

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Adaptive planning is crucial for head and neck proton therapy but lacks quantitative decision-making indicators.
• Current methods do not objectively guide when to adapt treatment plans.

Purpose of the Study:

• To establish a quantitative threshold for plan quality changes indicating the need for adaptive planning.
• To correlate plan quality differences with physician decisions in head and neck proton therapy.

Main Methods:

• Analyzed 167 patients' intensity-modulated proton therapy plans for oropharyngeal cancers.
• Utilized a percentile-based Daisy scoring system to assess plan quality differences.
• Employed generalized linear mixed models and physician review to evaluate adaptation necessity.

Main Results:

• A significant relationship was found between plan score differences and the need for adaptation (P=0.034).
• Plans requiring adaptation showed a mean score drop of 37.7%, versus 19.3% for acceptable plans.
• Clinical tumor volume and hotspot dose were key indicators for adaptation decisions.

Conclusions:

• A percentile-based Daisy scoring system provides a reliable threshold for adaptive planning decisions.
• This system can objectively identify when changes in plan quality necessitate adaptive proton therapy.