MRI for Prostate Cancer? If you Don’t See it, It’s Probably Not There

Multiparametric MRI of the prostate is once again in the news – the urological news, that is. A research group at Yale University School of Medicine[i] wondered, “If a man has a multiparametric MRI (mpMRI) of the prostate and it doesn’t show significant prostate cancer (PCa), what are the chances that it’s wrong?” This is an excellent question, given that studies have shown that mpMRI done by experts has roughly 98% accuracy in detecting significant cancer. And whether or not the PCa is significant has a huge bearing on whether the patient needs treatment, and how soon. In fact, a growing number of clinicians are recommending Active Surveillance, not immediate treatment, for patients with low-risk (insignificant) disease.

For the Yale study, the team identified 670 cases of men who had mpMRI between 2012-16. Out of that cohort, 100 men had no suspicion of significant prostate cancer (Gleason grade 3+4 or higher) based on their MRI results. To confirm this, the researchers conducted a 12-core template biopsy on every patient. They found 27% of the men had insignificant prostate cancer, that is, small low-risk tumors that mpMRI would be expected to not pick up.  3 of the men (3%) had Gleason 7 or higher detected by biopsy.

Based on this, the researchers wrote, ““Our results suggest that avoidance of systematic biopsy in patients with negative imaging results may be feasible.”[ii] This is good news for patients. It basically says that it’s well worth it to have a prostate mpMRI before undergoing a biopsy, because only when the scan shows an area suspicious for Gleason 7 or higher PCa should a biopsy be the next step. If the mpMRI does indicate the need for a biopsy, the best approach is to have it done inside the MRI in order to guide a minimum number of needles into the precise target for the most accurate diagnosis.

The study authors offer the most logical advice: “There is an approximately 3% chance of detecting clinically significant prostate cancer with systematic TRUS-guided biopsy in patients with no suspicious findings on mpMRI. This information should help guide recommendations to patients about undergoing systematic TRUS-guided biopsy when mpMRI is negative.”[iii] It’s always nice when the news is good.

[i] Lu AJ, Syed JS, Nguyen KA, Nawaf CB et al. Negative Multi-Parametric MRI of the Prostate Predicts Absence of Clinically Significant Prostate Cancer on 12-Core Template Prostate Biopsy. Urology. 2017 Mar 16. pii: S0090-4295(17)30247-9. doi: 10.1016/j.urology.2017.01.048. [Epub ahead of print]

[ii] Chernow, Jody. “Prostate Biopsy May be Avoidable if MRI Findings are Negative.” Mar. 23, 2017.

[iii] Lu et al., ibid.