As I spend time catching up with recent publications in my areas of specialty, it’s a time-saver to find a paper that reviews, summarizes and compares more than 40 studies. I thank Sugano, et al. (2021)[i] for doing all that work in “Comparative Effectiveness of Techniques in Targeted Prostate Biopsy.” It’s a bonus when the data they report supports our prostate cancer (PCa) services at the Sperling Prostate Center.
There’s more information in the article than I can cram into a single blog. It explains the difference between systematic vs. targeted biopsies. It covers targeted biopsy approaches (transrectal, transperineal) and biopsy guidance methods (transrectal ultrasound, cognitive fusion, software fusion, in-bore real-time MRI) and patient status (never had a biopsy or biopsy naive, previous negative biopsy, being monitored on Active Surveillance). Comparisons are then made in terms of detection rates of clinically significant PCa vs. clinically insignificant PCa. The entire article is available here.
The trend toward targeted biopsy
Many urologists still embrace the conventional systematic method using 12+ needles guided by transrectal ultrasound (TRUS). This method has high rates of overdetecting insignificant PCa while underdetecting or missing significant disease. It can be painful, and has side effect risks that include infection, blood in urine, or blood in sperm. To counter these downsides, there is an increasing trend toward targeted biopsy. With the use of MRI guidance, precision targeting requires fewer needles to go right to the core of suspicious areas. Not only does this reduce side effects, it produces more accurate diagnostic results. Thus, an effective biopsy has high diagnostic accuracy yet low rates of side effects.
Comparing fusion targeting vs in-bore MRI
I have posted numerous blogs about the flaws of TRUS guided biopsies. For this blog I want to cite a few comparison statistics from studies described in the Sugano article.
First, a word about software fusion. Computer-generated fusion incorporates MRI by co-registering image coordinates from a CD of a previous MRI prostate scan with live transrectal ultrasound. While fusion is commonly referred to as “MRI guidance”, I want to emphasize that MRI is only a portion of the guidance, and a static one at that. It’s not live! It’s not real time! Furthermore, it is susceptible to errors in co-registration (human error) patient positioning, and patient movement including breathing.
Also, “cognitive fusion” does not rely on software. Instead, a urologist mentally matches what he sees on an MRI CD with what he sees during an ultrasound exam; he’s picturing in his mind where the suspicious tumor is when he targets a needle into the gland using ultrasound guidance. Ultrasound shows where he’s placing needles, but he must picture the tumor in his mind’s eye because ultrasound is blind to tissue differences. It’s basically an educated guess. On the other hand, software fusion calculates where to place the needle(s) based on the coordinates entered by the doctor, and it maps placement when it shows the suggested needle trajectories on the computer monitor. This takes some of the guesswork out, but the burden of accurate co-registration still rests with the doctor.
Here are some sample statistics from the Sugano article to give you an idea of the effectiveness of cognitive fusion, software fusion, and in-bore targeting.
- Cognitive targeting + systematic bx vs. in-bore MRI targeting – One study involved 219 patients, 64 of whom had cognitive fusion + conventional systematic biopsy, and 155 had in-bore targeting. Cognitive + systematic had a positive diagnosis rate of 50%, while in-bore had a positive diagnosis rate of 65%. Cognitive missed 11% of low-grade tumors that were found by systematic biopsy. In-bore MRI targeted detected small lesions at a rate of 69% vs. 39% for cognitive + conventional. Keep in mind that in-bore involved a minimum number of needles compared to 12 or more needles for cognitive + systematic.
- Software fusion targeting vs. in-bore MRI-targeting – Another study found that software fusion had a positivity rate of 49% for clinically significant PCa vs. in-bore’s positivity rate of 61% for clinically significant disease. A third study demonstrated that in-bore had a higher rate of diagnosing clinically significant PCa and a lower rate of detecting insignificant disease than fusion; in addition, in-bore’s diagnostic accuracy resulted in lower rates of upgrading Gleason grade on prostatectomy. No one should go through surgery only to learn his PCa is worse than what the biopsy report said!
On balance, in-bore biopsies are more effective at diagnosing clinically significant PCa with fewer risks. Is there a downside? The authors raise the point that MRI is “costly and time-consuming, requiring an MRI suite and MRI-compatible equipment and supplies, and well as the expertise to use them.” On the other hand, the authors identify that faster MRI protocols like biparametric MRI, and one-stop appointments (a multiparametric MRI scan immediately followed by in-bore targeted biopsy) can improve costs. Also, Artificial Intelligence is contributing automatization of image reading to reduce radiologists’ workload.
The true value
Despite urologists’ objections over MRI expense, economic analysis has shown that the costs of repeat biopsies and treatment for their side effects add up, while the accuracy of in-bore biopsy saves medical dollars down the line. More importantly, the true value of a man’s life and its quality is at stake when inaccurate diagnosis leads to inappropriate treatment with potentially tragic consequences. In this light, there can be no doubt that in-bore targeting produces the most effective biopsy.
NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.
[i] Sugano D, Kaneko M, Yip W, Lebastchi AH et al. Comparative Effectiveness of Techniques in Targeted Prostate Biopsy. Cancers (Basel). 2021 Mar; 13(6): 1449.