Two problems face men who have a high PSA or abnormal digital rectal exam (DRE). First, they are often referred for a conventional TRUS needle biopsy of the prostate because there is suspicion of prostate cancer (PCa). Second, multiparametric MRI is considered too time-consuming and expensive for routine determination of the need for a biopsy. Because of these two factors, untold numbers of men undergo a TRUS biopsy that might have been avoided.
Many of those who have a biopsy will be told that the results were negative for PCa. Words like, “Good news, Mr. Smith. You don’t have prostate cancer!” bring welcome relief from worry. Unfortunately, about 30% of them will still have a high or rising PSA a year later, and will be sent back for another biopsy because the first one missed the tumor. In such cases, the European Association of Urology recommends that when PSA elevation continues, the patient’s next step should be a multiparametric MRI (mpMRI). If it reveals a suspicious area, an MRI-guided targeted biopsy into the region of interest should then be done.
You may wonder if it isn’t worth the extra time or money to do an mpMRI scan when the PSA or DRE is abnormal to begin with. This is a very good question, because repeat biopsies can have expensive, time-consuming consequences – not to mention putting patients at risk of harboring undetected disease that is growing or becoming more aggressive. Now, a research team led by Ivan Jambor, MD, may have found a way to make an mpMRI scan shorter and less expensive.[i] Their study involved 161 patients who had never had a biopsy but who had suspiciously high PSA values and/or abnormal DRE. The researchers developed what they called a biparametric MRI protocol (using just two parameters, no contrast agent and no endorectal coil). The two parameters were T2 weighted imaging (T2W) and diffusion weighted imaging (DWI); when combined, they are often considered the work horse of prostate MRI. See my blog at http://sperlingprostatecenter.com/combining-mri-parameters-better-t2-weighting-alone/.
The researchers used their MRI protocol to stratify men as very low suspicion, low suspicion, equivocal suspicion (could be either low or high) and high suspicion. Those in the first two categories had systematic biopsies, whereas those in the equivocal-to-high categories had targeted biopsies into the areas of suspicion seen on biparametric MRI. In terms of detecting clinically significant PCa (Gleason 3+4 or higher), the targeted biopsies had a detection rate of 11% compared with only 6% detection by systematic biopsy. There was also a 16% rate of upgrading patients to a higher risk category by targeted biopsy (16%) vs. 8% for systematic biopsy. The team calculated that if biopsy was done only on patients whose biparametric MRI revealed highly suspicious areas, about 24% of men with abnormal PSA or DRE could safely avoid having a biopsy and instead track PSA/DRE to signal a change that warrants a biopsy.
The research team expressed the hope that a faster, less expensive biparametric MRI protocol would encourage physicians to use prebiopsy MRI more routinely at the first rise in PSA or abnormal DRE.
[i] Jambor I, Boström PJ, Taimen P, Syvänen K, et al. Novel biparametric MRI and targeted biopsy improves risk stratification in men with a clinical suspicion of prostate cancer (IMPROD Trial). J Magn Reson Imaging. 2017 Feb 6. doi: 10.1002/jmri.25641. [Epub ahead of print]