The Case for Prostate Biopsies With MRI/US Fusion
Current standard of practice for initial prostate biopsy is 12 cores, with “hit rates” or cancer detection ranging from 25-40%. At Virginia Urology, our positive rate approaches 40%, so we’re doing pretty well compared to the rest of the country at this time. With post-biopsy infection rates also a hot topic, better biopsy results and less invasive means are a reasonable goal.
In my mind there are three goals of a prostate biopsy:
- Detect significant prostate cancer. This is first and foremost, and the current rates of detection are mediocre at best.
- Don’t miss high-risk cancers. Biopsy understaging is well established, and Gleason 6 cancers on biopsy may be higher risk Gleason 7 cancer on final evaluation. So the info that we’re getting on standard biopsy may be off the mark. We may also miss a cancer on the initial biopsy up to 20% of the time.
- Avoid complications from biopsy, such as sepsis or bacterial prostatitis (risk 2-7%). Multiple biopsies increase the risk for infection and even ED.
With these goals in mind, it may be time to consider targeted biopsies, with MRI-Ultrasound fusion technology as the lynchpin for development of better results.
As a fellow in the Urologic Branch of the National Cancer Institute (NCI), I had the privilege to work with DR. Peter Choyke in the prostate cancer arena, mainly with MRI guided brachytherapy. Since that time, Dr. Choyke and Peter Pinto, MD have helped develop the MRI-US fusion technology to allow assisted-imaging technology for better prostate biopsy yield (see PMID:23083875). Basically, a 3-T endorectal MRI is done and imaging of suspicious lesions are fused onto transrectal US images (in collaboration with Phillips Healthcare software) and biopsies obtained from concerning sites and traditionally. A recent study demonstrated a 23% advantage of sampling high-risk MRI sites by a targeted approach vs 12-core traditional sampling (53% + rate with fusion vs 30% + rate traditional biopsy). Whens stratified by MRI risk, intermediate and high risk detection rates were 67% and 89% respectively – improved vs current standards. MRI appeared to detect more cancer per core as well. Because with traditional biopsy, sampling of the peripheral zone is done, but the anterior horn and distal apex (periurethral) areas can be easily missed. This is where I believe this fusion technology may be worth its salt — visual evaluation of the whole gland with focused discriminatory sampling (If it ain’t relevant, it ain’t getting sampled). With higher risk lesions being detected the first time with adequate sampling to minimize understaging, the information needed to make a decision about treatment is enhanced and relevant and more sensitive. Moreover, with low-risk lesions (that may be clinically irrelevant anyway), the detection rate by both methods is low. This to me is a default watchful waiting program with added MRI reassurance that something relevant has not been missed, an additional insurance policy for the patient. This technology can also be applied to focal therapy and prostate cancer active surveillance as well.
At UCLA, Marks also reported on a novel system of 3-T MRI/US fusion biopsies in the clinic under local anesthesia (see PMID:23158413). They used Artemis, a novel spatial biopsy tracking system to enhance biopsy localization with memory. In their lower yield groups studied (active surveillance and repeat biopsy groups), targeted cancer detection was improved 21% vs 7% with standard biopsies. The 7% seems a bit low, as most AS patients get transition zone sampled or perhaps saturation approach if volume higher. Prostate cancer was found in 53% of patients, and 38% was Gleason 7 or greater, which is relevant disease in this lower risk cohort. Of the men with intermediate risk or greater cancers, 38% were only detected via the Artemis technology, ie they would have been missed on traditional sampling. This demonstrates further proof of principle with this type of technology, and the mapping program used will be relevant if repeat biopsies are needed or with focal therapy localization. Lastly, Hadashik et al, first used perineal biopsy platform in 2011 with the similar 3-T MRI pre-localization (see PMID:22014798). Results were impressive, with no infections via this approach. Prostate cancer detection was 59% and correlation of MRI to biopsy was 69%. OF MRI lesions that were deemed high risk, 23 of 24 patients had biopsy proven cancer. The perineal approach allows for improved detection in the anterior aspect of the prostate, and this may be an option if a high risk lesion is seen in this zone. If seen in the peripheral zone, transrectal US guided approach would be best. The point is we would not have known unless the MRI was done. Ultrasound by itself is a poor discriminator of cancer vs other (BPH, prostatitis, scar), therefore its sensitivity of detection is low.
In summary, new technology needs to be vetted, and these studies offer a novel paradigm shift in the development of improved detection of prostate cancer, and more importantly relevant cancers. This MRI/US fusion platform may sort out the life-threatening cancers from the ones we can observe, and I believe this is where its utility may lie. If the yield is higher per biopsy with this methodology, I could also foresee a potential improved cost differential in detection at least even with the addition of advanced technology versus traditional means. This fusion software technology can be of use to those of us in the trenches doing the biopsies, as it can be translated to the clinic and biopsies done similar to how we are doing now (local or sedation). I await the validation of some of these studies, and the potential improvement that it brings our patients. Furthermore, the benefits of this platform with safer selection of Active Surveillance patients, and improved Focal therapy localization and follow-up are also tangible and relevant. As a group, Virginia Urology performs more than 2500 prostate biopsies yearly. Our infection rate is low, and over 10,000 patients have trusted us for their prostate cancer treatments in the last 15 years, which says a lot. Thank you. We are investigating this technology and others to bring to the Virginia Urology Center in the near future.