There’s a quip that goes, “If fifty people tell you you’re drunk, fall over.” The point is obvious. When you know you’re outnumbered, back down.
Since the early 1990s, prostate needle biopsy using transrectal ultrasound (TRUS) guidance has been the reigning method for diagnosing prostate cancer (PCa). Compared to prior biopsy methods, it was a relative walk in the park. (For a rather bloodcurdling history of 20th century open biopsy methods before imaging guidance, read The Development of the Modern Prostate Biopsy.) Transrectal ultrasound not only made prostate biopsy less invasive, it also had economic advantages. The equipment is affordable for urology practices, and the procedure can be done in an office setting.
In its early days, TRUS biopsy involved taking three samples from each side of the prostate—total of six sites—so it was called a sextant biopsy. As time passed, it became clear from comparing biopsy reports with actual post-prostatectomy specimens that six needles did not sample enough of the gland, thereby missing or underdiagnosing PCa. Gradually 10-12 needles became standard, with many urologists preferring 12-14 needles. As a consequence, side effect risks—including infection—rose.
Introducing Magnetic Resonance Imaging (MRI)
The problem with TRUS guidance is its inability to identify suspicious areas within the gland. Ultrasound lacks the imaging power to define tissue differences, so needles were aimed according to a conceptual “grid” of the prostate, in hopes of a positive “hit.” In reality, as we now know, much insignificant PCa was picked up while significant PCa was missed. Since PCa can only be definitively diagnosed from tissue samples, a more precise way to identify needle placement for maximum diagnostic power was needed.
With the introduction of multiparametric MRI that can visually characterize tissue differences, doctors now had a tool for identifying suspicious areas to sample, and for guiding individual needles directly into those areas. However, as often happens, implementing this new approach met with objections:
“Have to get the patient to a radiology suite.”
“Urologists aren’t trained to interpret MRI scans.”
An “attractive alternative” to TRUS biopsy
Despite the resistance, evidence has been accumulating in favor of real-time MRI guidance for targeted prostate biopsies. An impressive May, 2019 journal article by Kasivisvanathan et al. compares MRI-targeted biopsy (MRI-TB) vs. systematic TRUS biopsy for detecting and diagnosing PCa.[i] I say impressive because the authors represent several authoritative academic, research and clinical urology centers in Europe. All centers/departments are urologic, so we can rule out a bias toward radiology.
The purpose of their work was “to compare the detection rates of clinically significant and clinically insignificant cancer by MRI-TB with those by systematic biopsy in men undergoing prostate biopsy to identify prostate cancer.” For their analysis, the authors compiled and analyzed results from 76 previously published clinical studies involving a total of 14,709 men! They included 68 prospective or retrospective studies with a paired design (MRI-TB compared with systematic TRUS biopsy) and 8 randomized controlled trials (men assigned randomly to either MRI-TB or TRUS).
They found that MRI-TB accurately detected more men with clinically significant PCa and fewer men with insignificant PCa than TRUS biopsy. Also, the proportion of needle cores that were positive for PCa was greater for targeted than systematic biopsy, demonstrating that directing biopsy needles into the heart of a suspicious area is more productive in gaining a true idea of tumor volume. They conclude that “MRI-TB is an attractive alternative diagnostic strategy to systematic biopsy.”
The patient’s (and urologist’s) best interest
What is the best thing a urologist can do for the patient as well as for him/herself? Obviously, it’s to make sure the patient receives the best PCa treatment. That means achieving the most strategic balance between cancer control and lifestyle issues. Matching the treatment to the disease is only possible when the most detailed portrait of the tumor has been obtained—which is achievable today only by integrating multiparametric MRI into the diagnostic pathway. Whether the treatment choice is surgery, radiation, ablation or Active Surveillance, if the patient is well-served, the doctor is too. Everyone wins when the diagnosis and treatment are done according to the patient’s best interest.
The Kasivisvanathan analysis, developed out of nearly 15,000 cases, is a solid step toward amassing the kind of numbers needed to persuade urologists that MRI is a patient’s best friend when it comes to detection and diagnosis. Hopefully, when TRUS finally recognizes it’s outnumbered, it will ultimately back down.
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
[i] Kasivisvanathan V, Stabile A, Neves JB, Giganti F et al. Magnetic Resonance Imaging-targeted Biopsy Versus Systematic Biopsy in the Detection of Prostate Cancer: A Systematic Review and Meta-analysis. Eur Urol. 2019 May 23.