MRI has many roles in prostate cancer (PCa), including use in biopsy-naïve men with elevated PSA, patients with a prior negative prostate biopsy, active surveillance patients, and patients with concern for possible disease recurrence following radiation or ablative therapy. Prostate MRI has expanded beyond T2-weighted imaging (T2WI) and is now augmented by diffusion-weighted imaging (DWI) and dynamic contrast-enhanced imaging (DCE) into what is known as multiparametric MRI (mpMRI).¹

mpMRI is considered the gold standard for imaging the prostate by many and is unique in that it has 3 mechanisms for soft tissue characterization. Unlike biparametric MRI (bpMRI), mpMRI has DCE, which involves IV contrast administration to the patient to evaluate prostatic tissue for perfusion behavior.^2–4 mpMRI is the basis of the Prostate Imaging Reporting and Data System, version 2, that scores lesions of the prostate for likelihood of harboring clinically significant PCa.^5,6 However, multiple drawbacks exist with mpMRI, such as cost, time to complete the study, and the impact of gadolinium-based contrast injection.^3,4,7,8

bpMRI is an alternative to mpMRI, only includes T2WI and DWI, and is defined by its dual-sequence noncontrast approach.⁴ There are multiple practical advantages with bpMRI. Comparative studies have demonstrated significantly shorter acquisition times relative to mpMRI, with some noting times of only 7 to 10 minutes to complete bpMRI.^9–11 Furthermore, other time-consuming tasks associated with mpMRI need to be considered such as IV access and contrast administration, which drive estimates for mpMRI completion to > 30 minutes and, in some cases, 45 minutes.¹² bpMRI also eliminates the potential risks of gadolinium deposition in the central nervous system. This deposition has been proven to accumulate over time and has unknown definitive significance, although it has been postulated to potentially have a detrimental impact.⁷ Cost is also a measurable advantage of bpMRI. Porter et al¹¹ modeled bpMRI and mpMRI and found 3 bpMRI studies could be completed in a 45-minute time frame relative to 1 mpMRI study during the same time, and that the gross profit margin of bpMRI was > $1500, resulting in an increase of > $10,700 for a 9-hour business day. While a paucity of head-to-head comparisons for interpretation times of mpMRI and bpMRI exists, there is some evidence that bpMRI may not be as dependent on radiographic interpreter experience.¹³ Di Campli et al reviewed 85 patients with elevated PSA and/or abnormal digital rectal examination who underwent bpMRI and mpMRI and saw no difference in the detection of clinically significant cancer for bpMRI based on reader experience,¹³ unlike in mpMRI, where the radiographic learning curve is well documented.¹⁴

The most important aspect of MRI in PCa is the ability to detect clinically significant disease, and current evidence demonstrates bpMRI is efficacious and equivalent relative to mpMRI. Rais-Bahrami et al demonstrated that bpMRI outperforms PSA in screening for clinically significant PCa and that combining bpMRI with PSA and PSA density (PSAD) increased the sensitivity, specificity, and negative predictive value to detect clinically significant PCa over PSA and PSAD alone.¹⁵ Similar findings have been replicated, notably concluding that combining bpMRI with other screening tools like PSA and PSAD is superior.¹⁶ Direct comparison of bpMRI to mpMRI has shown noninferiority in identifying clinically significant PCa. Sherrer et al reviewed mpMRI-ultrasound fusion prostate biopsy patients and compared pathology results to bpMRI and the DCE phase to assess if DCE added value to clinically significant PCa identification.¹⁷ In their analysis of 648 target lesions, only 1 case of clinically significant PCa was seen on DCE that was not seen on the T2WI sequence of bpMRI. Other research by Paesano et al has indicated that expert reading of bpMRI may prevent unnecessary prostate biopsies relative to mpMRIs interpreted by general radiologists and reduce detection of clinically insignificant PCa.¹⁸

Despite strong evidence that bpMRI is adequate in most clinical scenarios, there are still times where practitioners should recognize the added value of mpMRI with DCE, most often in patients with concern of intraprostatic PCa recurrence after prior radiotherapy or ablative therapy. One study reviewed 24 patients with prior radiation therapy for PCa and recurrence concern who subsequently underwent mpMRI and transrectal biopsy.¹⁹ In comparison to T2WI alone, adding DWI and DCE significantly increased the AUC to detect clinically significant PCa. Likewise, Roy et al used an 83-patient cohort and concluded that mpMRI provided a sensitivity nearing 100% after radiation therapy for clinically significant PCa.²⁰ Evidence is more limited for focal therapy, but some data suggest treatments like high-intensity focused ultrasound cause tissue disturbances that make detection of PCa recurrence specifically favorable on DCE.^21,22 The Figure demonstrates a clinical case where mpMRI added value to tumor recurrence identification relative to bpMRI alone, further validated with prostate-specific membrane antigen positron emission tomography imaging performed for systemic extraprostatic staging.

Looking forward, noncontrast prostate MRI will likely include bpMRI supplemented by other testing, such as biomarkers. One randomized control trial currently exists, where the decision to perform prostate biopsies was compared based on Stockholm3 risk scores and bpMRI.²³ Results were similar for the biomarker and bpMRI groups with the caveat that there was less identification of insignificant PCa and fewer biopsies done in the bpMRI cohort. Additionally, new noncontrast imaging studies hold promising avenues for research such as microultrasound imaging and histoscanning for optimizing diagnostic yield.

Ultimately, bpMRI has many advantages including time, cost, and less variation in interpretation, with noninferior oncologic diagnostic outcomes in most instances. These advantages are centered on the lack of contrast administration required. Nonetheless, there remain select roles for mpMRI in specific patient populations and clinical scenarios. With more options available now than ever before to physicians for diagnostic prostate imaging, variables like patient history, along with cost and time to both the patient and health care system, should be highly considered before ordering any diagnostic study.