Dataset Information

A biological modelling based comparison of radiotherapy plan robustness using photons vs protons for focal prostate boosting.

ABSTRACT:

Background and purpose

Focal tumour boosting is currently explored in radiotherapy of prostate cancer to increase tumour control. In this study we applied dose response models for both tumour control and normal tissue complications to explore the benefit of proton therapy (PT) combined with focal tumour boosting, also when accounting for inter-fractional motion.

Materials and methods

CT scans of seven patients fused with MRI-based index volumes were used. Two volumetric modulated arc therapy (VMAT) plans were created for each patient; one with conventional dose (77?Gy) to the entire prostate, and one with an additional integrated boost (total dose of 95?Gy) to the index lesion. Two corresponding intensity modulated PT (IMPT) plans were created using two lateral opposing spot scanning beams. All plans were evaluated using an MRI-based tumour control probability (TCP) model and normal tissue complication probability (NTCP) models for the rectum and bladder. Plan robustness was evaluated using dose re-calculations on repeat cone-beam CTs.

Results

Across all plans, median TCP increased from 86% (range: 59-98%) without boost to 97% (range: 96-99%) with boost. IMPT plans had lower rectum NTCPs (e.g. 3% vs. 4% for boost plans) but higher bladder NTCPs (20% vs. 18% for boost plans), yet only the bladder NTCPs remained different in the cone beam CT-based re-calculations.

Conclusions

Focal tumour boosting can be delivered with either VMAT or protons, and increases the predicted TCP. The small benefit of IMPT when assessing the planned dose distributions was lost when accounting for inter-fractional motion.

SUBMITTER: Pedersen J

PROVIDER: S-EPMC7807577 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Publications

A biological modelling based comparison of radiotherapy plan robustness using photons vs protons for focal prostate boosting.

Pedersen Jesper J Casares-Magaz Oscar O Petersen Jørgen B B JBB Rørvik Jarle J Bentzen Lise L Andersen Andreas G AG Muren Ludvig P LP

Physics and imaging in radiation oncology 20180401

<h4>Background and purpose</h4>Focal tumour boosting is currently explored in radiotherapy of prostate cancer to increase tumour control. In this study we applied dose response models for both tumour control and normal tissue complications to explore the benefit of proton therapy (PT) combined with focal tumour boosting, also when accounting for inter-fractional motion.<h4>Materials and methods</h4>CT scans of seven patients fused with MRI-based index volumes were used. Two volumetric modulated ...[more]

PMID: 33458397

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Project description:BACKGROUND AND PURPOSE:Incidental irradiation of normal brain tissue during radiotherapy is linked to cognitive decline, and may be mediated by damage to healthy cortex. Non-coplanar techniques may be used for cortical sparing. We compared normal brain sparing and probability of cortical atrophy using 4? radiation therapy planning vs. standard fixed gantry intensity-modulated radiotherapy (IMRT). MATERIAL AND METHODS:Plans from previously irradiated brain tumor patients ("original IMRT", n?=?13) were re-planned to spare cortex using both 4? optimization ("4?") and IMRT optimization ("optimized IMRT"). Homogeneity index (HI), gradient measure, doses to cortex and white matter (excluding tumor), brainstem, optics, and hippocampus were compared with matching PTV coverage. Probability of three grades of post-treatment cortical atrophy was modeled based on previously established dose response curves. RESULTS:With matching PTV coverage, 4? significantly improved HI by 27% (p?=?0.005) and gradient measure by 8% (p?=?0.001) compared with optimized IMRT. 4? optimization reduced mean and equivalent uniform doses (EUD) to all standard OARs, with 14-15% reduction in hippocampal EUD (p???0.003) compared with the other two plans. 4? significantly reduced dose to fractional cortical volumes (V50, V40 and V30) compared with the original IMRT plans, and reduced cortical V30 by 7% (p?=?0.008) compared with optimized IMRT. White matter EUD, mean dose, and fractional volumes V50, V40 and V30 were also significantly lower with 4? (p???0.001). With 4?, probability of grade 1, 2 and 3 cortical atrophy decreased by 12%, 21% and 26% compared with original IMRT and by 8%, 14% and 3% compared with optimized IMRT, respectively (p???0.001). CONCLUSIONS:4? radiotherapy significantly improved cortical sparing and reduced doses to standard brain OARs, white matter, and the hippocampus. This was achieved with superior PTV dose homogeneity. Such sparing could reduce the probability of cortical atrophy that may lead to cognitive decline.

Dataset Information

A biological modelling based comparison of radiotherapy plan robustness using photons vs protons for focal prostate boosting.

Background and purpose

Materials and methods

Results

Conclusions

Publications

A biological modelling based comparison of radiotherapy plan robustness using photons vs protons for focal prostate boosting.

Similar Datasets

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