Date Added: 11/06/2015

Date Updated: 11/06/2015

MRI screening for prostate cancer

Specialties: Renal disease & urology - Oncology & radiotherapy - Mens Health & Sexual Health

Technology Type: Devices - Programmes

Stage of development: Other

Stage of EAA: Assessment Complete

Description, patients and keywords:
MRI uses a combination of radio-waves and powerful magnet to produce detailed images of soft tissues within the human body. The advantage of MRI as opposed to other X-ray based radiology scans is the ability of producing the image without the usage of ionising radiation. This makes this technology very attractive to requesting general practitioners and specialists, subject to the contraindications in people with metal and electronic implant devices. A typical MRI scan lasts between 20 minutes and 1.5 hours, depending on the complexity of the scan and the technical capabilities of the scanner, in particular the magnet strength. The length of the scan in conjunction with the closed environment of full body scanner; means claustrophobia may play a part in the patient suitability for a MRI scan of the male pelvis.(1) The closed nature of the MRI scanner is demonstrated in Figure 1 (left side).
MRI has spread rapidly through hospitals and private practices due to the superior tissue characterisation capabilities. In recent times, innovative pulse sequences have being developed that overcome sensitivity and specificity limitations of conventional MRI.(2) This technique involves combining at least two functional pulse sequences (diffusion-weighted, dynamic contrast enhanced or spectroscopic imaging) that can be analysed together in a multi-parametric framework. An example of the integrated multi-parametric sequences can be seen in the right side of Figure 1. Within this protocol, MRI has improved accuracy to detect and stage prostate cancer. Outside of clinical trial settings, spectroscopy is sometimes omitted from the multi-parametric work-up, due to its high cost in terms of additional time required, expertise and additional software demands to execute the scan effectively.(3)

If a lesion is detected with multi-parametric MRI, further classification and grading with biopsy is required. Pathologists grade prostate cancers according to the Gleason system. The Gleason sum score helps determine the future prognosis for men and to decide suitable treatments. A higher score indicates less differentiation or ability to recognise normal prostate glands, representing more aggressive tumour and worse prognosis. The most common scores reported on biopsy are Gleason 6-8, with Gleason 6 or lower considered low risk, 7 intermediate risk and 8 and above high risk. Patient management and treatment will be determined largely by this biopsy outcome. A tumour of Gleason 6 can be managed initially with, Gleason 7 and Gleason 8+ tumours require active treatment.(4) There are currently three techniques available for pathologists using MRI-based biopsies:
1. Magnetic resonance-guided biopsy: the only technique utilising a direct, in-bore approach. This results in the greatest reproducibility with the most expensive cost. Given that this procedure is performed within the live magnet, the approach will be restricted to an interventional radiologist;
2. MRI/Ultrasound fusion-guided biopsy: involves software fusion of MRI images with ultrasound images (Figure 2) to spatially coordinate biopsy location using a floor or table mounted grid apparatus. The biopsy approach is either performed transrectal or transperineal to the preference of urologist; and
3. MRI/Ultrasound cognitive- informed biopsy: the simplest technique involving visual correlation of MRI image and ultrasound image to manually direct biopsy.

Recent systematic reviews have suggested that MRI and MR-based biopsy can reliably detect prostate tumours, providing critical information on tumour location, volume, grade and stage.(7, 8) As such there is likely to be an increasing role of imaging the prostate using MRI in the areas of:
• Early detection and screening for prostate cancer;
• Guiding patient selection for biopsy: shift to image-based approach;
• Selecting men for repeat biopsy; and
• Active surveillance: of identified low risk prostate cancer that would otherwise receive radical surgery and/or radiotherapy.

This report is work in progress and should not be used for external distribution without permission from the originating agency. Users should be aware that reports are based on information available at the time of research and often on a limited literature search.