Abstract
Purpose
We aimed to determine whether multiple-CT (MCT) optimization of intensity-modulated
proton therapy (IMPT) could improve plan robustness to anatomical changes and therefore
reduce the additional need for adaptive planning.
Methods and materials
Ten patients with head and neck cancer who underwent IMPT were included in this retrospective
study. Each patient had primary planning CT (PCT), a first adaptive planning CT (ACT1),
and a second adaptive planning CT (ACT2). Selective robust IMPT plans were generated
using each CT data set (PCT, ACT1, and ACT2). Moreover, a MCT optimized plan was generated
using the PCT and ACT1 data sets together. Dose distributions optimized using each
of the four plans (PCT, ACT1, ACT2, and MCT plans) were re-calculated on ACT2 data.
The doses to the target and to organs at risk were compared between optimization strategies.
Results
MCT plans for all patients met all target dose and organs-at-risk criteria for all
three CT data sets. Target dose and organs-at-risk dose for PCT and ACT1 plans re-calculated
on ACT2 data set were compromised, indicating the need for adaptive planning on ACT2
if PCT or ACT1 plans were used. The D98% of CTV1 and CTV3 of MCT plan re-calculated on ACT2 were both above the coverage criteria.
The CTV2 coverage of the MCT plan re-calculated on ACT2 was worse than ACT2 plan.
The MCT plan re-calculated on ACT2 data set had lower chiasm, esophagus, and larynx
doses than did PCT, ACT1, or ACT2 plans re-calculated on ACT2 data set.
Conclusions
MCT optimization can improve plan robustness toward anatomical change and may reduce
the number of plan adaptation for head and neck cancers.
Keywords
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Article Info
Publication History
Published online: September 26, 2019
Accepted:
September 11,
2019
Received in revised form:
September 9,
2019
Received:
January 4,
2019
Identification
Copyright
© 2019 Elsevier B.V. All rights reserved.
