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Ruling Out Clinically Significant Prostate Cancer with Negative Multi-Parametric MRI: Beyond the Abstract

Prostate multi-parametric MRI (mpMRI) combines the high tissue-resolution sequences with several functional sequences to help clinicians better identify and risk-assess suspicious lesions.  A “negative”, or PI-RADS category 1, study is one without any distinct regions of suspicion.  According to edition of PI-RADS (v.2) guidelines, a patient with PI-RADS category 1 should have a “very low likelihood” of harboring any clinically significant PCa.1  We wanted evaluate this “very low likelihood” definition, and to provide quantitative data to validate or refute this.  We believe determining if a negative MRI study is sufficient to rule-out significant cancer (Gleason 7 or higher) has both scientific merits, and clinical impact for many men undergoing PCa evaluation.  The ability to rule-out high-risk PCa with non-invasive imaging could allow select patients to avoid or delay unnecessary procedures.

To examine this, we evaluated 114 men from our institution with a PI-RADS 1 prostate mpMRI and biopsy within one year of imaging.  A 3.0 T MRI was used to acquire all images, and an endorectal coil was used in the majority of protocols.  Overall, 88 (77.2%) patients in our cohort had no cancer detected upon biopsy.  Of the 26 patients with cancer, the majority (84.6%) had Gleason 6 (3+3), and few (15.4%) had Gleason ≥7 cancer.  The NPV in the entire cohort was 96.5%, 100% in the biopsy naïve cohort (n=20), 100% in the prior negative biopsy cohort (n=53), and 90% in the prior positive cohort (n=4).  All 4 patients detected with Gleason ≥7 cancer had prior positive biopsy and were on active surveillance at the time of MRI.

While there is excellent data on the cancer detection rate of patients with MR visible lesions, less is known in patients with negative mpMRI.  Despite optimized image acquisition and expert interpretation, it has been suspected by some that significant cancers may still be missed on imaging.  In our current study, we found very low rates of clinically significant cancer on systematic 12-core biopsy overall.  Of the 114 men with negative mpMRI who had undergone biopsy, less than 4% were found to have clinically significant cancer.  While a negative mpMRI cannot unequivocally rule out significant PCa, the likelihood of finding significant PCa identified in patients with negative mpMRIs is reliably low (NPV 96.5%).

Our findings may be particularly useful for patients who have had previous negative biopsy but are unsure of its reliability.  None of the 53 patients with prior negative biopsy had any clinically significant cancer.  Of the three patients within this group who did have cancer, all had low-risk Gleason 6 (3+3) disease and could remain on active surveillance.  Our data suggest patients with negative mpMRI, especially those with previously negative biopsy, can avoid repeat prostate biopsy.  


Co-Authors: Julie Y. An, Abhinav Sidana, Baris Turkbey
 
Reference: 

1Weinreb JC, Barentsz JO, Choyke PL, et al. PI-RADS Prostate Imaging - Reporting and Data System: 2015, Version 2. Eur Urol. 2016;69(1):16-40.

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