A novel model to correlate hydrogel spacer placement, perirectal space creation, and rectum dosimetry in prostate stereotactic body radiotherapy

The SpaceOAR hydrogel is employed to limit rectal radiation dose during prostate radiotherapy. We identified a novel parameter - the product of angle θ and hydrogel volume - to quantify hydrogel placement. This parameter predicted rectum dosimetry and acute rectal toxicity in prostate cancer patient...

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Bibliographic Details
Published in:Radiation oncology (London, England) England), 2018-10, Vol.13 (1), p.192-192, Article 192
Main Authors: Hwang, Mark E, Black, Paul J, Elliston, Carl D, Wolthuis, Brian A, Smith, Deborah R, Wu, Cheng-Chia, Wenske, Sven, Deutsch, Israel
Format: Article
Language:English
Subjects:
Asymmetry
Background radiation
Cancer
Cancer therapies
Care and treatment
CAT scans
Clinical trials
Computed tomography
Computer simulation
Correlation
Dosimeters
Dosimetry
FDA approval
Health aspects
Health risks
Hydrogels
Learning curves
Men
Methods
Parameter identification
Patients
Placement
Prostate cancer
Radiation
Radiation dosage
Radiation therapy
Radiotherapy
Rectal toxicity
Rectum
SpaceOAR hydrogel
Stereotactic body radiotherapy
Symmetry
Toxicity
Urology
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Summary:The SpaceOAR hydrogel is employed to limit rectal radiation dose during prostate radiotherapy. We identified a novel parameter - the product of angle θ and hydrogel volume - to quantify hydrogel placement. This parameter predicted rectum dosimetry and acute rectal toxicity in prostate cancer patients treated with stereotactic body radiotherapy to 36.25 Gy in 5 fractions. Twenty men with low- and intermediate-risk prostate cancer underwent hydrogel placement from 2015 to 2017. Hydrogel symmetry was assessed on the CT simulation scan in 3 axial slices (midgland, 1 cm above midgland, 1 cm below midgland). Two novel parameters quantifying hydrogel placement - hydrogel volume and angle θ formed by the prostate, hydrogel, and rectum - were measured, and the normalized product of θ and hydrogel volume calculated. These were then correlated with perirectal distance, rectum maximum 1-3 cc point doses (rD 1-3 cc), and rectum volumes receiving 80-95% of the prescription dose (rV80-95%). Acute rectal toxicity was recorded per RTOG criteria. In 50% of patients, hydrogel placement was symmetric bilaterally to within 1 cm of midline in all three CT simulation scan axial slices. Lateral hydrogel asymmetry
ISSN:1748-717X
1748-717X
DOI:10.1186/s13014-018-1135-6