By: Dan Sperling, MD

For a quarter century, the diagnostic pathway for prostate cancer has looked like this:

Abnormal PSA/DRE ? TRUS biopsy ? Diagnosis (positive or negative for prostate cancer)

Originally, the TRUS (transrectal ultrasound-guided) biopsy consisted of a sextant biopsy, meaning three areas on each side of the gland were sampled for a total of six needles. As time went on, the inadequacy of this method was demonstrated by the number of men who were told they did not have prostate cancer (PCa), only to have continued abnormal PSA’s and DRE’s, and repeat biopsies until cancer was finally “hit” by the biopsy needle. In many cases, the cancer’s aggression had by then increased, making it more difficult to cure.

Gradually, the recommended number of needles increased from 8 to 10 to 12 or more. Another approach, the transperineal mapping biopsy, proved more precise due to the high number of samples taken every 5 mm throughout the gland; but this was expensive, since it was done in a surgical setting under general anesthesia. A compromise, the so-called “saturation biopsy” done in a urologist’s office, took 20-24 transrectal samples; many patients were not adequately “numbed up” and suffered during the procedure. Today, the most common prostate biopsy is a TRUS biopsy averaging 10-14 samples. Still, false negative rates as high as 30% continue to be reported in the literature.

A January, 2015 study published by an Italian research team offers evidence of the superiority of multiparametric MRI (mpMRI) for detecting tumors and guiding biopsy sampling.[i] It is especially noteworthy due to the size: 1140 patients whose screening results indicated potential PCa were divided into two groups. Each group of 570 patients was assigned to one of two different diagnostic pathways. The men in Group A had a TRUS-guided random biopsy. Those in Group B first had an mpMRI followed by a TRUS-guided targeted-and-random biopsy. The authors note that the accuracy of mpMRI in the diagnosis of PCa was calculated using prostatectomy as the standard of reference.

• Group A – At the initial biopsy, 215 patients were found to be positive for PCa. However, the 355 patients whose biopsies were negative eventually had mpMRI scans, and 208 were found to have cancer-suspicious lesions (missed by TRUS biopsy). The remaining 147 patients had unremarkable mpMRI scans. Thus, combining the positive TRUS biopsies and the suspicious MRIs, a total of 423 patients were considered to have PCa.
• Group B – Based on mpMRI, 440 patients had positive findings, and were subsequently biopsied using the TRUS-guided targeted (into the suspicious area) + random biopsy method. PCa was diagnosed in 417 at first biopsy. The remaining 130 patients had unremarkable mpMRI and biopsy findings; however, this group then underwent saturation biopsies which detected insignificant cells not picked up on mpMRI (Gleason 6 PCa or precancerous lesions).

In Group B, mpMRI showed 97% accuracy for the diagnosis of PCa. The authors concluded, “The proportion of men with clinically significant PCa is higher among those randomized to mp-MRI/biopsy vs. those randomized to TRUS-guided biopsy; moreover, mp-MRI is a very reliable tool to identify patients to schedule in active surveillance.”

This is an exciting study because it underscores the merits of an imaging technology that can revolutionize prostate biopsies. In addition to improved diagnostic accuracy and the potential to prescribe biopsies only when mpMRI finds suspicious lesions, mpMRI detection of PCa offers the possibility of more cost-effective medicine with higher quality of life for patients. See https://sperlingprostatecenter.com/new-study-favors-mri-guided-biopsy-trus/ for a summary of a Dutch study published by Rooij et al.[ii] In all respects, it is becoming more difficult to defend use of the conventional TRUS biopsy when a better technology is available.

[i] Panebianco V, Barchetti F, Sicarra A et al. Multiparametric magnetic resonance imaging vs. standard care in men being evaluated for prostate cancer: A randomized study . Urol Oncol. 2015 Jan;33(1):17.e1-7.

[ii] De Rooij M, Crienen S, Witjes JA et al. Cost-effectiveness of magnetic resonance (MR) imaging and MR-guided targeted biopsy versus systematic transrectal ultrasound-guided biopsy in diagnosing prostate cancer: a modeling study from a health care perspective. Eur Urol. 2014 Sep;66(3):430-6.