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Review
. 2019 Apr 1:18:68-73.
doi: 10.1016/j.ctro.2019.03.006. eCollection 2019 Sep.

Prostate cancer - Advantages and disadvantages of MR-guided RT

Julia Murray  1 , Alison C Tree  1
Affiliations
Review

Prostate cancer - Advantages and disadvantages of MR-guided RT

Julia Murray et al. Clin Transl Radiat Oncol. .

Abstract

External beam radiotherapy for prostate cancer is an optimal treatment choice for men with localised prostate cancer and is associated with long term disease control in most patients. Image-guided prostate radiotherapy is standard of care, however, current techniques can include invasive procedures with imaging of poor soft tissue resolution, thus limiting accuracy. MRI is the imaging of choice for local prostate cancer staging and in radiotherapy planning has been shown to reduce target volume and reduce inter-observer prostate contouring variability. The ultimate aim would be to have a MR-only workflow for prostate radiotherapy. Within this article, we discuss these opportunities and challenges, relevant due to the increasing availability of MR-guided radiotherapy. Prospective multi-centre studies are underway to determine the feasibility of MR-guided prostate radiotherapy and daily adaptive replanning. In parallel, development and adaptation of the existing radiotherapy multidisciplinary workforce is essential to enable an efficient and effective MR-guided radiotherapy workflow. This technology potentially provides us with the anatomical and biological information to further improve outcomes for our patients.

Keywords: ADT, androgen deprivation therapy; CBCT, cone beam CT; CTV, clinical target volume; Daily adaptive replanning; GI, gastrointestinal; GU, genitourinary; IGRT, image-guided radiotherapy; MRI; MRI, magnetic resonance imaging; OAR, organ at risk; PTV, planning target volume; Prostate cancer; RTOG, radiation therapy oncology group; Radiotherapy; mpMRI, multi-parametric MRI.

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Figures

Fig. 1
Fig. 1
Improved soft tissue contrast with MR (top panel) compared to CT (bottom panel). The MR image shown was taken prior to treatment on the MR Linac.
Fig. 2
Fig. 2
Daily MR images (axial slice) used for replanning on two separate days (top and bottom panels) showing little change of the prostate and rectum. The prostate is contoured in red. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 3
Fig. 3
Daily axial MR images for online replanning showing bowel to the left of the rectum on one day (top panel, mid femoral head axial level), bowel inserting between the seminal vesicles on another day (middle panel, mid femoral head level) and bowel displacing the bladder to the right (bottom panel, above femoral head level).
Fig. 4
Fig. 4
Workflow outline for the Unity at the Royal Marsden, UK (image courtesy of Helen McNair and Alex Dunlop).
Fig. 5
Fig. 5
Images of a test plan for the MR Linac delivering 19 Gy to the whole prostate with 21 Gy to the dominant tumour lesion, whilst respecting HDR rectal and bladder constraints (image courtesy of Jonathan Mohajer).
See this image and copyright information in PMC

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