Radiotherapy dose escalation using pre-treatment diffusion-weighted imaging in locally advanced rectal cancer: a planning study

Nathan Hearn; Alexandria Leppien; Patrick O'Connor; Katelyn Cahill; Daisy Atwell; Dinesh Vignarajah; Myo Min

doi:10.1093/bjro/tzad001

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Radiotherapy dose escalation using pre-treatment diffusion-weighted imaging in locally advanced rectal cancer: a planning study

Journal article

Open access

Peer reviewed

Radiotherapy dose escalation using pre-treatment diffusion-weighted imaging in locally advanced rectal cancer: a planning study

Nathan Hearn, Alexandria Leppien, Patrick O'Connor, Katelyn Cahill, Daisy Atwell, Dinesh Vignarajah and Myo Min

BJR - Open, Vol.6(1), pp.1-8

2024

DOI: https://doi.org/10.1093/bjro/tzad001

PMID: 38352181

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Abstract

Diffusion-weighted imaging

Dose escalation

Rectal cancer

Radiotherapy

MRI

Objectives Diffusion-weighted MRI (DWI) may provide biologically relevant target volumes for dose-escalated radiotherapy in locally advanced rectal cancer (LARC). This planning study assessed the dosimetric feasibility of delivering hypofractionated boost treatment to intra-tumoural regions of restricted diffusion prior to conventional long-course radiotherapy. Methods Ten patients previously treated with curative-intent standard long-course radiotherapy (50 Gy/25#) were re-planned. Boost target volumes (BTVs) were delineated semi-automatically using 40th centile intra-tumoural apparent diffusion coefficient value with expansions (anteroposterior 11 mm, transverse 7 mm, craniocaudal 13 mm). Biased-dosed combined plans consisted of a single-fraction volumetric modulated arc therapy flattening-filter-free (VMAT-FFF) boost (phase 1) of 5, 7, or 10 Gy before long-course VMAT (phase 2). Phase 1 plans were assessed with reference to stereotactic conformality and deliverability measures. Combined plans were evaluated with reference to standard long-course therapy dose constraints. Results Phase 1 BTV dose targets at 5/7/10 Gy were met in all instances. Conformality constraints were met with only 1 minor violation at 5 and 7 Gy. All phase 1 and combined phase 1 + 2 plans passed patient-specific quality assurance. Combined phase 1 + 2 plans generally met organ-at-risk dose constraints. Exceptions included high-dose spillage to bladder and large bowel, predominantly in cases where previously administered, clinically acceptable non-boosted plans also could not meet constraints. Conclusions Targeted upfront LARC radiotherapy dose escalation to DWI-defined is feasible with appropriate patient selection and preparation. Advances in knowledge This is the first study to evaluate the feasibility of DWI-targeted upfront radiotherapy boost in LARC. This work will inform an upcoming clinical feasibility study.

Details

Title: Radiotherapy dose escalation using pre-treatment diffusion-weighted imaging in locally advanced rectal cancer: a planning study
Authors: Nathan Hearn (Corresponding Author) - University of the Sunshine Coast, Queensland, Thompson Institute
Alexandria Leppien - Sunshine Coast University Hospital
Patrick O'Connor - Sunshine Coast University Hospital
Katelyn Cahill - University of the Sunshine Coast, Queensland, Thompson Institute
Daisy Atwell - University of the Sunshine Coast, Queensland, Thompson Institute
Dinesh Vignarajah - Sunshine Coast University Hospital
Myo Min - University of the Sunshine Coast, Queensland, Thompson Institute
Publication details: BJR - Open, Vol.6(1), pp.1-8
Publisher: Oxford University Press
Date published: 2024
DOI: 10.1093/bjro/tzad001
ISSN: 2513-9878
PMID: 38352181
Grant note: This research is supported by the Sunshine Coast Hospital and Health Service SERTF-Wishlist 2021 Collaborative Research Grant Scheme.
Organisation Unit: Thompson Institute
Language: English
Record Identifier: 991008898602621
Output Type: Journal article

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