By: Dan Sperling, M.D.

I have frequently mentioned in my series of articles that even today’s most sophisticated MRI is not yet able to definitively diagnose prostate cancer. Only a biopsy can withdraw the tissue required to provide an accurate Gleason grade. (NOTE: The grade of a tumor indicates how aggressive it is; if you’re not familiar with Gleason grade, check out the explanation at http://www.phoenix5.org/grading.html)

On the other hand, a PSA blood test cannot determine who REALLY needs a biopsy and who doesn’t. Thus, countless men undergo a TRUS biopsy every year, only to not find any cancer, or to find insignificant cancer that may be simply monitored. Can MRI help to identify which men should undergo a biopsy? That is the question raised by a new study published by a distinguished team from University College London Hospitals (England), Fayoum University (Egypt) and other outstanding medical institutions[i].

Background: MRI technology is rapidly improving, including more powerful magnets and various methods of analyzing the images for clues about suspicious areas. These are called “parameters.” When we refer to Multiparametric MRI (mpMRI), it means we use several parameters to help us understand the images we’re looking at. Cancerous tumors have different properties than normal tissue, including how dense they are, how much water they contain, how elastic the tissue is, and whether there’s a separate blood supply to the tumor. Each of these parameters gives us different information that we pull together to determine if what we see on the images is healthy tissue or a tumor.

The new research study I mentioned above address the question of whether a pre-biopsy mpMRI of the prostate can determine the need for biopsy. The authors set up a side-by-side comparison of mpMRI cancer detection with template-guided transperineal mapping biopsy (TMB). Why TMB and not TRUS? It’s because of the detection flaws inherent in 10-core TRUS biopsies. Unlike a transrectal biopsy, TMB uses a rigid guidance grid placed against the perineum, or skin between the scrotum and the rectum, giving a non-rectal access route to the prostate. While the patient is under anesthesia, a doctor inserts biopsy needles, one at a time, through holes in the grid to extract tiny snips of tissue at 5mm intervals throughout the gland. Each snip is fixed onto a slide and its exact location noted. Because of how thorough the sampling is, the authors call TMB “a robust reference standard” for purposes of this study.

The study enrolled 129 men whose PSA indicated suspicion of prostate cancer, but who had no previous biopsy. Each patient underwent an mpMRI with and without contrast prior to biopsy. No endorectal coil was used. Experienced radiologists evaluated the images and assigned a numeric value using the European Consensus Guidelines as follows:

• 1 – clinically significant disease is highly unlikely to be present
• 2 – clinically significant disease is unlikely to be present
• 3 – clinically significant disease is equivocal
• 4 – clinically significant disease is likely to be present
• 5 – clinically significant disease is highly likely to be present

These ratings were recorded prior to TMB, so the readers were blinded to the reference test.

Each patient then had a TMB. Pathologists analyzed the tissue samples and assigned a Gleason grade to those positive for the presence of cancer. The results from the mpMRI and TMB were then compared and analyzed.

Keeping in mind that the purpose of the study was to explore the merits of mpMRI as a way to determine whether or not a biopsy is indicated, the authors concluded, “MpMRI demonstrated encouraging diagnostic performance characteristics in detecting and ruling out clinically significant prostate cancer in men at risk, who were biopsy naive.” In our own experience, we have been successful in using mpMRI to identify who needs a biopsy, and if one is necessary, our 3T MRI equipment provides excellent guidance for precise prostate biopsy with a reduced number of needles.