It seems intuitive, if not obvious, that superior imaging of the prostate gives precise information to guide a biopsy needle into a cancerous tumor. The typical ultrasound imaging used by urologists in their offices is inferior to magnetic resonance imaging (MRI). Ultrasound-guided transrectal (TRUS) biopsy has a minimum 35% chance of missing cancer. If our own 3T multiparametric MRI (mpMRI) reveals a suspicious area, we do a highly targeted biopsy guided by real-time MRI: less invasive, more accurate.
While prostate biopsy is still largely “owned” by urology, there is a way for urologists to use MRI information to help direct their TRUS biopsies. I found a published study that is encouraging for patients who don’t have access to a real-time MRI-guided biopsy. It’s not perfect, but it beats the alternative.
The study was conducted by a team from a university medical center in Seoul, Korea.[i] It involved 669 patients with persistently high PSA but who had a previous negative TRUS biopsy. The study’s purpose was to compare the cancer detection rates of a TRUS biopsy informed by MRI images (MRI group = 171 patients) vs. TRUS biopsy without access to MRI images (non-MRI group = 498 patients). Both groups then had a TRUS re-biopsy; all tissue samples were submitted for pathology analysis and diagnosis. Of the total group, 129 (19.3%) were diagnosed with prostate cancer.
As far as the detection rate differences between the MRI and non-MRI groups, what do you think the research team found? It’s no surprise that the pre-biopsy MRI group had a higher rate of detection:
- MRI group – 33.3% diagnosed
- Non-MRI group – 14.5% diagnosed
The authors therefore recommend that “MRI should be considered prior to re-biopsy in patients with previous negative biopsy and persistently high PSA.”
This study shows that providing advance MRI-based knowledge to a urologist allows him to mentally integrate that information with his ultrasound guidance in order to selectively aim the needle gun into the suspicious area. Even though ultrasound can’t depict the exact tumor, the urologist has a preferential sense of where to aim based on the MRI. We see from this study how it can improve the performance of a conventional TRUS biopsy.
We don’t yet live in a medical world where every man with risk for/suspicion of prostate cancer has equal access to a 3T mpMRI as a logical first step in detection. In addition, the number of U.S. locations offering a real-time MRI-guided biopsy is still relatively small. From a urology perspective, very few urologists have MRI-ultrasound fusion software, and apparently the Korean university medical center likewise did not. Still, publishing the news that an MRI before repeat biopsy—for that matter, before any biopsy—improves biopsy success can help demonstrate to the urological community how advanced imaging could help their patients. Good news indeed!
[i] Park BK, Jeon SS, Park B et al. Comparison of re-biopsy with preceded MRI and re-biopsy without preceded MRI in patients with previous negative biopsy and persistently high PSA. Abdom Imag. 2014 Nov 4. DOI:10.1007/s00261-014-0245-3. Epub ahead of print.