Role Of MRI In Targeting Prostate Cancer In Patients With Previous Negative Biopsies And Elevated Prostate-Specific Antigen Levels

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Main Category: Prostate / Prostate Cancer
Also Included In: Urology / Nephrology;  Cancer / Oncology;  MRI / PET / Ultrasound
Article Date: 12 Jun 2009 - 3:00 PDT

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UroToday.com - In this recent review we highlight the important role of MRI in assisting in the detection of prostate cancer (CaP) in men with previous negative biopsies and elevated prostate-specific antigen levels. ^[1]

We summarised the current data on the efficacy of MRI for targeting cancer, compared with biopsies, in patients with previous negative prostate biopsies and persistently elevated prostate-specific antigen (PSA) levels. The key clinical question is how many men benefit by having had prostate cancer detected purely because of the MRI-targeted, as opposed to standard scheme, biopsies.

We reviewed all available databases for prospective studies in patients having MRI and prostate biopsy with previous negative biopsies and persistently elevated PSA levels.

Six studies fulfilled the selection criteria, with 215 patients in all; in these studies, the cancer-detection rate at repeat biopsy was 21-40%. For MRI or combined MRI/MR spectroscopy, the overall sensitivity for predicting positive biopsies was 57-100%, the specificity 44-96% and the accuracy 67-85%. In five studies, specific MRI-targeted biopsies and standard cores were taken, with a significant proportion (34/63, 54%) having cancer detected purely because of the MRI-targeted cores.

The value of endorectal MRI and MR spectroscopy in patients with elevated PSA levels and previous negative biopsies to target peripheral zone tumours appears to be significant. Although more data obtained with current technologies are needed, published results to data are encouraging. A comparison study and cost-benefit analysis of MRI-targeted versus saturation biopsy in this group of patients would also be ideal, to delineate any advantages.

MRI localisation of CaP has several important goals:

• 1. Detection - to allow for directed biopsies by clinicians by locating the CaP rather than just undertaking random biopsies, particularly in patients having had prior negative biopsies or those having discordant PSA and prior low-volume disease on active surveillance.


• 2. Staging and treatment planning- this is important when counselling patients prior to radical prostatectomy regarding the applicability of surgery and the need for possible adjuvant treatments as well as for guiding radiation treatment plans. Today, MRI may also allow selection of candidates for focal therapy. ^[2]


• 3. Monitoring of treatment effects

Since our review, two very recent additional important papers dealing with MRI detection of prostate cancer have been or are about to be published. Firstly, a recent multicentre trial of 110 men that assessed the accuracy of MRI against whole-mount pathological specimens for peripheral zone tumours found MR spectroscopy and T2-weighted MRI to be similar at 58% and 60% by AUC. ^[3]

In the other study using dynamic contrast enhanced MRI (DCE-MRI), which also had pathological confirmation, ^[4] the overall result for detection was excellent with 64/83 having a positive MRI and identification of the index cancer lesion in two thirds of cases. In the second study, the limitation came in detecting extremely small foci of cancer at <0.5cc. Over this level MRI had a sensitivity of 86% and specificity of 94% with an AUC of 0.87. As in other studies, smaller foci were difficult to detect.

These recent publications perform similarly to our institution where we were able to demonstrate accuracy with an AUC of 89%, using T2 combined with diffusion-weighted imaging (DWI). ^[5]

Unfortunately, MRI literature regarding CaP is still plagued by differences in accuracy between centres. Still, overall, results are improving and in appropriately selected patients, MRI is finally proving to be beneficial. However, larger studies need to confirm the improved results across a variety of populations.

Certainly at present, MRI remains sensitive only to larger tumours but is currently useful for selected groups: those men with prior negative biopsy or where a discordant PSA exists in the context of low volume disease, staging particularly where T3 disease is suspected and choosing candidates for focal therapy. With the development of 3T MRI scanners and new MRI sequences and parameters being better understood (e.g. DWI, when to use contrast, spectroscopy etc) the future for MRI in Cap is exciting and is likely to be important.

References

^[1] Lawrentschuk N, Fleshner N. The role of magnetic resonance imaging in targeting prostate cancer in patients with previous negative biopsies and elevated prostate-specific antigen levels. BJU Int. 2009 Mar: 103:730-3
^[2] Tareen B, Sankin A, Godoy G, Temkin S, Lepor H, Taneja SS. Appropriate candidates for hemiablative focal therapy are infrequently encountered among men selected for radical prostatectomy in contemporary cohort. Urology. 2009 Feb: 73:351-4; discussion 4-5
^[3] Weinreb JC, Blume JD, Coakley FV, et al. Prostate cancer: sextant localization at MR imaging and MR spectroscopic imaging before prostatectomy--results of ACRIN prospective multi-institutional clinicopathologic study. Radiology. 2009 Apr: 251:122-33
^[4] Authors Pending. Dynamic Contrast-Enhanced MRI Evaluation of Intraprostatic Prostate Cancer. Correlation with Radical Prostatectomy Specimens. Urology. 2009: In press
^[5] Haider MA, van der Kwast TH, Tanguay J, et al. Combined T2-weighted and diffusion-weighted MRI for localization of prostate cancer. AJR Am J Roentgenol. 2007 Aug: 189:323-8

Written by Nathan Lawrentschuk and Neil E. Fleshner as part of Beyond the Abstract on UroToday.com

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