Highlights
- •MRI provides superior visualization of abdominal anatomy compared to CBCT.
- •MRgRT plan adaptation mitigates organ motion and provides superior dosimetry.
- •Several patients had meaningful reductions in OAR violations with online adaptation.
- •Not all liver SBRT patients materially benefit from online adaptation.
- •Higher plan quality may permit safe dose escalation without compromising quality.
Abstract
Purpose/objective
Online Adaptive Radiotherapy (ART) with daily MR-imaging has the potential to improve
dosimetric accuracy by accounting for inter-fractional anatomical changes. This study
provides an assessment for the feasibility and potential benefits of online adaptive
MRI-Guided Stereotactic Body Radiotherapy (SBRT) for treatment of liver cancer.
Materials/methods
Ten patients with liver cancer treated with MR-Guided SBRT were included. Prescription
doses ranged between 27 and 50 Gy in 3–5 fx. All SBRT fractions employed daily MR-guided
setup while utilizing cine-MR gating. Organs-at-risk (OARs) included duodenum, bowel,
stomach, kidneys and spinal cord. Daily MRIs and contours were utilized to create
each adapted plan. Adapted plans used the beam-parameters and optimization-objectives
from the initial plan. Planning target volume (PTV) coverage and OAR constraints were
used to compare non-adaptive and adaptive plans.
Results
PTV coverage for non-adapted treatment plans was below the prescribed coverage for
32/47 fractions (68%), with 11 fractions failing by more than 10%. All 47 adapted
fractions met prescribed coverage. OAR constraint violations were also compared for
several organs. The duodenum exceeded tolerance for 5/23 non-adapted and 0/23 for
adapted fractions. The bowel exceeded tolerance for 5/34 non-adaptive and 1/34 adaptive
fractions. The stomach exceeded tolerance for 4/19 non-adapted and 1/19 for adaptive
fractions. Accumulated dose volume histograms were also generated for each patient.
Conclusion
Online adaptive MR-Guided SBRT of liver cancer using daily re-optimization resulted
in better target conformality, coverage and OAR sparing compared with non-adaptive
SBRT. Daily adaptive planning may allow for PTV dose escalation without compromising
OAR sparing.
Graphical abstract
Graphical Abstract
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Article info
Publication history
Published online: August 09, 2020
Accepted:
July 20,
2020
Received in revised form:
June 24,
2020
Received:
February 28,
2020
Identification
Copyright
© 2020 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
