Two new studies demonstrate improved biopsy accuracy by using either 3 Tesla MRI (3T MRI) or multiparametric MRI (mpMRI) to detect suspicious areas in the prostate gland.
A study out of Germany was designed to test the diagnostic performance of mpMRI compared with a systematic transrectal ultrasound (TRUS) guided biopsy.[i] Their research involved 35 patients, each of whom had a history of persistently elevated or rising PSA and at least one previous negative TRUS biopsy. All of them underwent mpMRI and were found to have a lesion suspicious for prostate cancer according to the PI-RADS scoring system (see Dr. Sperling’s explanation of PI-RADS at https://sperlingprostatecenter.com/pi-rads-score/ and his comments on its accuracy at https://sperlingprostatecenter.com/testing-pi-rads-accuracy/). An average of three MRI-targeted biopsies was taken from each lesion; a TRUS biopsy was then performed by an independent urologist who was blind to the MRI findings. The tissue samples were analyzed by a pathology lab for tumor location and whether they were clinically significant according to the team’s criteria. The biopsy detection rates were:
MRI – 46% (16 out of 35 patients)
TRUS – 23% (8 out of 35 patients)
The MRI-guided biopsy detected cancer in all eight of the patients whose TRUS biopsy found the disease, and all tumors found by the MRI biopsies had at least one criterion for disease significance. In addition, the prostate cancer lesions had been given high PI-RADS scores than any benign lesions that were picked up by biopsy. The authors concluded not only that MRI-guided biopsy (MR-GB) is more effective than TRUS, but also that “PI-RADS scores give additional information and could be part of the decision-making process when considering retrial biopsy. Additional systematic biopsy [by TRUS] can be omitted in patients undergoing targeted MR-GB.”
A Korean study with a larger population had a different design but achieved the same goal in demonstrating that MRI provides superior information over ultrasound in guiding placement of biopsy needles.[ii] Their purpose was to compare TRUS re-biopsy in patients whose previous 3T MRI images were available vs. TRUS re-biopsy in patients with no previous 3T MRI. Between January 2007 and May 2011, 669 patients at their center in Seoul, Korea had a TRUS re-biopsy because of at least one earlier negative biopsy and a history of elevated PSA. The 3T MRI group consisted of 171 patients (average 10.6 cores per biopsy, total cores 1818), whereas 498 patients had no MRI before their re-biopsy (average 11.3 cores taken, total cores 5631). The MRI information on the 171 men suggested preferential placement of needles, even though the biopsy was done under ultrasound guidance (no real-time MRI or MRI/fusion). The results were reported for each group in terms of number of patient with biopsy-proven cancer as well as the number of cancer-positive cores. The results were:
|MRI group||Non-MRI group|
|Overall detection||33.3% (57/171)||14.5% (72/498|
|Number of positive cores||9.2% (167/1818)||3.2% (179/5631)|
Based on this data the authors concluded, “Re-biopsy with preceded MRI yields higher cancer detection rate and positive core rate than re-biopsy without preceded MRI. MRI should be considered prior to re-biopsy in patients with previous negative biopsy and persistently high PSA.”
Taken together, these studies show that imaging on powerful magnetic resonance equipment provides superior intelligence for planning and carrying out prostate biopsies. Although the Korean study did not utilize real-time MRI guidance for either group of patients, their TRUS re-biopsies performed on the men with previous 3T MRI images were more fruitful than those on the other group. On the other hand, the results of the German study suggested to the author that systematic TRUS re-biopsies could be skipped provided that PI-RADS scored images and MRI-guided targeted biopsy was used together.
[i] Kaufmann S, Kruck S, Kramer U, Gatidis S et al. Direct Comparison of Targeted MRI-Guided Biopsy with Systematic Transrectal Ultrasound-Guided Biopsy in Patients with Previous Negative Prostate Biopsies. Urol Int. 2014 Sep 13. [Epub ahead of print]
[ii] Park BK, Jeon SS, Park B, Park JJ 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 Imaging. 2014 Nov 4. [Epub ahead of print]