Multiparametric magnetic resonance imaging (mpMRI) is a specific MRI test used to detect and evaluate prostate cancer. It requires additional radiologist training and sequences not routinely performed in anatomic imaging, such as diffusion-weighted and dynamic contrast-enhanced imaging.¹ The National Comprehensive Cancer Network and the American Urological Association support using mpMRI for risk stratification before the first prostate biopsy, to perform targeted prostate biopsy, and in active surveillance.^2,3

Accuracy

The prostate imaging reporting and data system, second revision (PI-RADSv2) provides standardized interpretation and reporting of mpMRI.¹ A score between 1 and 5 is assigned by a radiologist (1 suggests that a clinically significant cancer is highly unlikely, and 5 suggests that it is highly likely). In a systematic review of 21 studies including 3,857 patients, the PI-RADSv2 tool (using a threshold score of 3 or 4) had a pooled sensitivity of 0.89 (95% CI, 0.86 to 0.92) and specificity of 0.73 (95% CI, 0.60 to 0.83) for the detection of prostate cancer.⁴ 

Inclusion of mpMRI information into a multivariate risk-prediction calculator improves the accuracy of cancer risk assessment and can assist in shared decision-making regarding management options.⁵ 

The strongest support for prebiopsy mpMRI has been derived from a systematic review of 15 studies (n = 2,293) in which mpMRI plus targeted biopsy was compared with transrectal ultrasound (TRUS)–guided systematic biopsy alone.⁶ By targeting suspicious areas of the prostate, the median rate of significant prostate cancer detection was 33% with mpMRI vs. 24% with biopsy alone. The targeted approach was also more efficient, requiring only nine core biopsies instead of 37. In addition, only 2% of clinically significant cancer was missed with mpMRI vs. 9% with TRUS-guided biopsy. Therefore, prebiopsy mpMRI can improve the diagnostic yield of a patient's first prostate biopsy.

Benefit

In a randomized controlled trial of 1,532 patients with prostate-specific antigen levels of 3 ng per mL (3 mcg per L) or greater, clinically significant prostate cancer was diagnosed in a similar percentage of patients who had mpMRI plus targeted biopsy as those who had TRUS-guided systematic biopsy alone (21% vs. 18%; risk difference = 3%; 95% CI, −1% to 7%). Additionally, clinically insignificant cancer was detected less often in the mpMRI plus targeted biopsy group compared with the TRUS-guided systematic biopsy group (4% vs. 12%; risk difference = −8%; 95% CI, −11% to −5%).⁷ 

A prospective cohort of 172 patients in whom cancer was suspected despite previous negative biopsies underwent mpMRI plus targeted biopsy and TRUS-guided systematic biopsy. Targeted biopsy detected clinically significant prostate cancer (Gleason score of 7 or more) more often than systematic biopsy (16% vs. 9%; P = .01).⁸ 

Based on improved risk assessment with the use of mpMRI and the test's high sensitivity, there is future potential to avoid unnecessary biopsies in patients with a low-risk result (PI-RADS score of 2 or less). Widespread adoption of this approach is not yet recommended because of dependence on operator experience and significant interobserver variability.⁹ Longer-term studies demonstrating the optimal biopsy threshold and safety are needed.

Harms

In 2017, the U.S. Food and Drug Administration started requiring a warning with gadolinium-based contrast agents because they may be partially retained in brain tissue for months to years after use.¹⁰ The only established complication of gadolinium-based contrast is nephrogenic systemic fibrosis, which affected up to 0.07% of patients with stage 4 or 5 chronic kidney disease in one large meta-analysis.¹¹ The long-term consequences of gadolinium retention are otherwise unknown and require further safety studies. 

Prostate cancer overdiagnosis remains a problem, but studies suggest that it is improved with the use of mpMRI.⁹

Cost

Studies suggest that mpMRI could be cost-effective at $23,483 per quality-adjusted life-year, although this conclusion depends on the assumption that a negative mpMRI result could be used to safely avoid biopsy.¹² 

Coding for MRI-TRUS targeted biopsy is complicated. The test is considered investigational by many insurance carriers, and there is no specific Current Procedural Terminology (CPT) code for it.¹³ CPT codes for the MRI and 3D rendering are billed by a radiologist, whereas the codes that urologists use for a biopsy are not changed by the use of mpMRI. The added radiologic costs and related CPT codes are listed in Table 1.¹⁴