Dataset Information

Dose to medium in head and neck radiotherapy: Clinical implications for target volume metrics.

ABSTRACT:

Background and purpose

In radiotherapy dose calculation, advanced type-B dose calculation algorithms can calculate dose to medium (D_m ), as opposed to Type-B algorithms which compute dose to varying densities of water (D_w ). We investigate the impact of D_m on calculated dose and target coverage metrics in head and neck cancer patients.

Methods and materials

We reviewed 27 successfully treated (disease free at two-years post-(chemo)radiotherapy) human papillomavirus-associated (HPV) oropharyngeal cancer (ONC) patients treated with IMRT. Doses were calculated with Type-B and Linear Boltzman Transport Equation (LBTE) algorithms in a commercial treatment planning system, with the treated multi-leaf collimator patterns and monitor units. Coverage for primary Gross Tumour Volume (GTVp), high dose Planning Target Volume (PTV) (PTV_High), mandible within PTV_High (Mand???PTV) and PTV_High excluding bone (PTV-bone) were compared between the algorithms.

Results

Dose to 95% of PTV_High with LBTE was on average 1.1?Gy/1.7% lower than with Type-B (95%CI 1.5-1.9%, p?r?=?-0.81). Dose to 98% of the GTVp was 0.9?Gy/1.3% lower with LBTE compared with Type-B (95%CI 1.1-1.5%, p?ConclusionIn OPC treated with IMRT, D_m results in significant reductions in dose to bone in high dose PTVs. Reported GTVp dose was reduced, but by a lower magnitude. Reduced coverage metrics should be expected for OPC patients treated with IMRT, with dose reductions limited to regions of bone.

SUBMITTER: Hardcastle N

PROVIDER: S-EPMC7807679 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Publications

Dose to medium in head and neck radiotherapy: Clinical implications for target volume metrics.

Hardcastle Nicholas N Montaseri Atousa A Lydon Jenny J Kron Tomas T Osbourne Glen G Casswell Georgina G Taylor David D Hall Lisa L McDowell Lachlan L

Physics and imaging in radiation oncology 20190701

<h4>Background and purpose</h4>In radiotherapy dose calculation, advanced type-B dose calculation algorithms can calculate dose to medium (<i>D<sub>m</sub></i> ), as opposed to Type-B algorithms which compute dose to varying densities of water (<i>D<sub>w</sub></i> ). We investigate the impact of <i>D<sub>m</sub></i> on calculated dose and target coverage metrics in head and neck cancer patients.<h4>Methods and materials</h4>We reviewed 27 successfully treated (disease free at two-years post-(ch ...[more]

PMID: 33458286

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Project description:Larynx may alternatively serve as a target or organs at risk (OAR) in head and neck cancer (HNC) image‐guided radiotherapy (IGRT). The objective of this study was to estimate IGRT parameters required for larynx positional error independent of isocentric alignment and suggest population‐based compensatory margins. Ten HNC patients receiving radiotherapy (RT) with daily CT on‐rails imaging were assessed. Seven landmark points were placed on each daily scan. Taking the most superior‐anterior point of the C5 vertebra as a reference isocenter for each scan, residual displacement vectors to the other six points were calculated postisocentric alignment. Subsequently, using the first scan as a reference, the magnitude of vector differences for all six points for all scans over the course of treatment was calculated. Residual systematic and random error and the necessary compensatory CTV‐to‐PTV and OAR‐to‐PRV margins were calculated, using both observational cohort data and a bootstrap‐resampled population estimator. The grand mean displacements for all anatomical points was 5.07 mm, with mean systematic error of 1.1 mm and mean random setup error of 2.63 mm, while bootstrapped POIs grand mean displacement was 5.09 mm, with mean systematic error of 1.23 mm and mean random setup error of 2.61 mm. Required margin for CTV‐PTV expansion was 4.6 mm for all cohort points, while the bootstrap estimator of the equivalent margin was 4.9 mm. The calculated OAR‐to‐PRV expansion for the observed residual setup error was 2.7 mm and bootstrap estimated expansion of 2.9 mm. We conclude that the interfractional larynx setup error is a significant source of RT setup/delivery error in HNC, both when the larynx is considered as a CTV or OAR. We estimate the need for a uniform expansion of 5 mm to compensate for setup error if the larynx is a target, or 3 mm if the larynx is an OAR, when using a nonlaryngeal bony isocenter.PACS numbers: 87.55.D‐, 87.55.Qr

Dataset Information

Dose to medium in head and neck radiotherapy: Clinical implications for target volume metrics.

Background and purpose

Methods and materials

Results

Publications

Dose to medium in head and neck radiotherapy: Clinical implications for target volume metrics.

Similar Datasets

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