According to the National Institute for Health and Care Excellence (NICE) guidelines, mpMRI should be considered for men with a negative TRUS guided biopsy, to determine whether another biopsy is needed. The National Comprehensive Cancer Network (NCCN) guidelines state that mpMRI should be considered when biopsy results are either benign, or atypia, suspicious for cancer is demonstrated, or high-grade prostatic intraepithelial neoplasia is witnessed.
Additional imaging modalities have been introduced, including the prostate shear wave elastography, and the 29 MHz micro-ultrasound, all demonstrating very optimistic results and high accuracy. These can either replace the mpMRI or more likely, complement it.
Next, Dr. Hammerer discussed the role of systematic vs. targeted biopsies. The combination of both targeted and systematic biopsies have been shown to diagnose a higher percentage of men with clinically localized significant prostate cancer, as seen in figure 1. This percentage seems to increase with more aggressive disease. When comparing mpMRI followed by MRI guided biopsy to mpMRI followed by TRUS guided biopsy, it is clear that MRI guided biopsy misses significant prostate cancer especially in the medial and posterior zones of the prostate, while TRUS guided biopsy miss significant cancer especially in the anterior and lateral zones, as seen in figure 2.
Figure 1 – Difference between systematic, targeted, and their combination in the diagnosis of prostate cancer:
Figure 2 – Where is significant prostate cancer missed after an MRI targeted and a TRUS biopsy:
The PRECISION trial1 compared men with a regular TRUS biopsy to men undergoing mpMRI, and only if positive, undergoing a biopsy. The mean age was 64, with a mean PSA of 6.7 ng/ml, 15% of the patients had an abnormal digital rectal examination, and 19% of the patients had a positive family history. The results clearly demonstrated an advantage for the mpMRI arm with 12% difference in the diagnosis of clinically significant cancer (38% vs 26%) and 13% lower rate of diagnosis of clinically insignificant cancer (9% vs. 22%). A total of 28% of the patients avoided a biopsy in this trial. The biopsy in the mpMRI arm entailed a median of only 4 cores, with fewer complications, more significant cancer diagnosed and less insignificant cancer diagnosed. The mpMRI has been shown to have a negative predictive value of 72%, a positive predictive value of 69%, a specificity of 47% and sensitivity of 87%.
The next question discussed is what to do for patients who have had a negative mpMRI. Dr. Hammerer believes that non-invasive follow-up based on confirmatory MRI and PSA measurements is a viable option for selected patients. Systematic biopsies cannot be routinely omitted after a negative mpMRI, especially in young patients with a positive family history, and strong clinical suspicion of prostate cancer, so that we do not miss clinically significant MRI-silent tumors.
Important goals for the future include figuring out the role of mpMRI in active surveillance. We also need to understand patients’ needs and try to significantly shorten the MRI examination time. Lastly, in patients who have a contraindication to a mpMRI, the role of PET PSMA needs to be expanded.
In summary, an imaging-guided approach is an important part of a prostate cancer diagnosis. TRUS is still the basic most standard evaluation tool, and TRUS-guided biopsy is still the gold standard for the first biopsy in 2018. MRI fusion biopsy is recommended for men undergoing a re-biopsy in an attempt to identify clinically significant prostate cancers.
Presented by: Peter Hammerer, MD, Braunschweig Municipal Hospital
1. NEJM 2018; 378: 1767-1777
Written By: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre Twitter: @GoldbergHanan at the 38th Congress of the Society of International Urology - October 4- 7, 2018 - Seoul, South Korea