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Review
. 2021 Feb 25:11:637591.
doi: 10.3389/fonc.2021.637591. eCollection 2021.

MR-Guided Adaptive Radiotherapy for Bladder Cancer

Adham Hijab  1   2 , Boris Tocco  1   2 , Ian Hanson  1   2 , Hanneke Meijer  3 , Christina Junker Nyborg  4 , Anders Smedegaard Bertelsen  5 , Robert Jan Smeenk  3 , Gillian Smith  2 , Jeff Michalski  6 , Brian C Baumann  6 , Shaista Hafeez  1   2
Affiliations
Review

MR-Guided Adaptive Radiotherapy for Bladder Cancer

Adham Hijab et al. Front Oncol. .

Abstract

Radiotherapy has an important role in the curative and palliative treatment settings for bladder cancer. As a target for radiotherapy the bladder presents a number of technical challenges. These include poor tumor visualization and the variability in bladder size and position both between and during treatment delivery. Evidence favors the use of magnetic resonance imaging (MRI) as an important means of tumor visualization and local staging. The availability of hybrid systems incorporating both MRI scanning capabilities with the linear accelerator (MR-Linac) offers opportunity for in-room and real-time MRI scanning with ability of plan adaption at each fraction while the patient is on the treatment couch. This has a number of potential advantages for bladder cancer patients. In this article, we examine the technical challenges of bladder radiotherapy and explore how magnetic resonance (MR) guided radiotherapy (MRgRT) could be leveraged with the aim of improving bladder cancer patient outcomes. However, before routine clinical implementation robust evidence base to establish whether MRgRT translates into improved patient outcomes should be ascertained.

Keywords: MR guided radiotherapy; MR-linac; MRI; adaptive radiotherapy; bladder cancer.

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Conflict of interest statement

BCB reports personal fees from Mevion, personal fees from Mevion/Sanofi, outside the submitted work. SH reports non-financial support from Elekta (Elekta AB, Stockholm, Sweden), non-financial support from Merck Sharp & Dohme (MSD), personal fees and non-financial support from Roche outside the submitted work. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Localized MIBC as evaluated on T2W and DWI with the associated parameter settings for 1.5T MRI. 70 year old male with known T3 N0 M0 bladder cancer, tumour is present at the left ureteric orifice (extending posteriorlaterally) (A) contrast enhanced CT scan, axial slice through pelvis, (B) axial T2W (large field of view) showing hypo intense lesion, (C) axial T2W small field of view (D) corresponding ADC map, (E) axial DWI at b-value 0, (F) axial DWI at b-value 750.
Figure 2
Figure 2
Online pre-treatment CBCT and MR (T2W) images. Bladder tumour at left bladder wall as seen on axial a), sagittal b), and coronal c) views of the pelvis on corresponding CBCT and T2W taken on the MR-Linac, here urine appears bright and tumour dark/hypointense.
Figure 3
Figure 3
Overview of the principal workflow components of online reoptimization using MRgRT.
See this image and copyright information in PMC

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