Magnetic resonance imaging in active surveillance-a modern approach

Abstract

In recent years, active surveillance has been increasingly adopted as a conservative management approach to low and sometimes intermediate risk prostate cancer, to avoid or delay treatment until there is evidence of higher risk disease. A number of studies have investigated the role of multiparametric magnetic resonance imaging (mpMRI) in this setting. MpMRI refers to the use of multiple MRI sequences (T2-weighted anatomical and functional imaging which can include diffusion-weighted imaging, dynamic contrast enhanced imaging, spectroscopy). Each of the parameters investigates different aspects of the prostate gland (anatomy, cellularity, vascularity, etc.). In addition to a qualitative assessment, the radiologist can also extrapolate quantitative imaging biomarkers from these sequences, for example the apparent diffusion coefficient from diffusion-weighted imaging. There are many different types of articles (e.g., reviews, commentaries, consensus meetings, etc.) that address the use of mpMRI in men on active surveillance for prostate cancer. In this paper, we compare original articles that investigate the role of the different mpMRI sequences in men on active surveillance for prostate cancer, in order to discuss the relative utility of the different sequences, and combinations of sequences. We searched MEDLINE/PubMed for manuscripts published from inception to 1^st December 2017. The search terms used were (prostate cancer or prostate adenocarcinoma or prostatic carcinoma or prostate carcinoma or prostatic adenocarcinoma) and (MRI or NMR or magnetic resonance imaging or mpMRI or multiparametric MRI) and active surveillance. Overall, 425 publications were found. All abstracts were reviewed to identify papers with original data. Twenty-five papers were analysed and summarised. Some papers based their analysis only on one mpMRI sequence, while others assessed two or more. The evidence from this review suggests that qualitative assessments and quantitative data from different mpMRI sequences hold promise in the management of men on active surveillance for prostate cancer. Both qualitative and quantitative approaches should be considered when assessing mpMRI of the prostate. There is a need for robust studies assessing the relative utility of different combinations of sequences in a systematic manner to determine the most efficient use of mpMRI in men on active surveillance.

Keywords: Prostate cancer; active surveillance; magnetic resonance imaging (MRI); prostate.

Figure 1

Bilateral tumour of the peripheral zone of the prostate (arrows) on T2-weighted imaging (A), diffusion weighted imaging (B), apparent diffusion coefficient map (C) and dynamic contrast-enhanced imaging (D). The tumour in the right mid gland (0.5 cc) lies between 7–8 o’clock (5/5 Likert scale). The tumour in the left mid gland (0.1 cc) lies between 4–5 o’clock and abuts the capsule (5/5 Likert scale). They both show low signal intensity (i.e., dark) on T2-weighted imaging (A) and apparent diffusion coefficient map (C), and high-signal intensity (i.e., bright) on diffusion-weighted (B) and dynamic contrast-enhanced (D) imaging.

Figure 2

Tumour of left mid gland of the prostate (arrows) on T2-weighted imaging (A), diffusion weighted imaging (B), apparent diffusion coefficient map (C) and dynamic contrast-enhanced imaging (D). The ill-defined lesion (10 mm) is bridging the transitional and peripheral zones, and lies between 4–5 o’clock (5/5 Likert scale). It shows low signal intensity (i.e., dark) on T2-weighted imaging (A) and apparent diffusion coefficient map (C), and high-signal intensity (i.e., bright) on diffusion-weighted (B) and dynamic contrast-enhanced (D) imaging.

Figure 3

Flow diagram showing the outcome of the initial searches resulting in the full studies included in the review. MpMRI, multiparametric magnetic resonance imaging; AS, active surveillance; T2-WI, T2-weighted imaging; DWI, diffusion-weighted imaging.