Abstract
The purpose of this study was to investigate the dosimetric impact of weight loss
in head and neck (H&N) patients and examine the effectiveness of adaptive planning.
Data was collected from 22 H&N cancer patients who experienced weight loss during
their course of radiotherapy. The robustness of Intensity Modulated Radiation Therapy
(IMRT) and Volumetric Modulated Arc Therapy (VMAT) treatment plans were compared including
the potential need for replanning. The dosimetric impact of weight loss was evaluated
by calculating a verification plan for each patient on an assessment CT scan taken
during the course of treatment. Using a regression analysis, significance was tested
for the dosimetric change in target volumes and 10 specific organs at risk (OAR) using
an anatomical separation difference in the H&N at corresponding levels. For both the
IMRT and VMAT plans, a significant correlation was found for the dose to 5% of the
high risk Planning Target Volume (PTV) (D5), dose to 95% of the intermediate risk PTV and Clinical Target Volume (CTV) (D95), and the percentage of the pharynx receiving 65 Gy. An independent t-test was also
performed for each metric in the VMAT and IMRT plans showing the dose to 95% of the
intermediate risk PTV as significant. No quantitative method for finding the threshold
of anatomical separation difference requiring a replan was established. Based on the
increase in dose to organs at risk and increased target coverage due to separation
loss, it was concluded that adaptive radiotherapy may not always be necessary when
alignment of bony anatomy and remaining soft tissue is within tolerance. Physician
judgment and preference is needed in such situations.
Keywords
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Article info
Publication history
Published online: June 17, 2019
Accepted:
May 21,
2019
Received in revised form:
April 16,
2019
Received:
December 5,
2018
Identification
Copyright
Published by Elsevier Inc. on behalf of American Association of Medical Dosimetrists.
