MP-MRI could prevent patients from undergoing unnecessary prostate biopsies
When it comes to prostate cancer, many agree that the prostate-specific antigen (PSA) test does not necessarily reign supreme (1). But if that’s the case, what should a responsible doctor do instead to rule out the possibility of dangerous disease? One option is a transrectal ultrasound-guided (TRUS) biopsy – but this procedure is invasive and can lead to infection, or several weeks of rectal or urethral bleeding. Although the biopsy can aid in diagnosing disease, its undesirable effects and the burden it places on hospitals means it is only often used when absolutely necessary. What’s the alternative? There’s one potential answer: multiparametric-magnetic resonance imaging (MP-MRI), according to a team of UK-based researchers who found that the technology could be an effective triage test to help reduce unnecessary TRUS biopsies (2). To learn more about their research, we talked with first author and consultant urologist Hashim U. Ahmed.
Why did you decide to focus on MP-MRI?
There was a palpable lack of robust evidence for the use of MP-MRI in diagnosing prostate cancer. Many papers were retrospective, comparing MP-MRI with surgical specimens (which meant that all men had to have cancer on biopsy and then choose surgery), or they compared MP-MRI to TRUS biopsy (which we know is an inaccurate comparison). These methodological biases led to considerable uncertainty and skepticism about the performance of MP-MRI. This meant that practice was slow to change and there would be little traction on a wide level.
We conducted a number of studies comparing MP-MRI to template mapping biopsies, which sample the entire prostate every 5 mm and can be used in almost all men (reducing selection bias). These studies were single-center, expert academic, and all but one was retrospective. Both our studies and those conducted by other groups (3)(4) showed that MP-MRI had excellent performance characteristics, but further evidence was needed.
What do your findings mean for prostate cancer biopsies?
Patients, clinicians, and hospitals now have level I evidence to demonstrate that MP-MRI before a first biopsy improves the chances of finding significant cancer that might otherwise be missed. For those wishing to avoid a first biopsy, MP-MRI beforehand can rule out significant disease with a high degree of probability, allowing men to safely enter clinical and serum PSA monitoring.
Do you believe that imaging will play a larger role in the future of diagnostics?
We must seriously consider changing our practice across all healthcare settings to institute an imaging test – MP-MRI in this instance – before a biopsy. It is what we do for all other solid organ cancers and we now have robust evidence for a similar diagnostic pathway in prostate cancer.
Further work is needed to evaluate the targeting of MRI areas. There are different ways of deploying the biopsy needle to suspicious areas, such as having the operator estimate the lesion’s location, using devices that fuse the MRI with ultrasound, or carrying out biopsies during the MRI itself. The detection rates and cost-effectiveness of these various approaches requires additional study.
Further work is also needed to see if liquid biomarkers could help identify men at risk before having MP-MRI, in order to reduce the costs and capacity issues that many healthcare settings may have with the new technique.
MP-MRI could also be used as a screening tool instead of PSA blood testing in high-risk populations like minority ethnicities or those with a family history of the disease. I am currently starting a study in relation to these factors.
- R McGuigan, “The Great Prostate Debate”, The Pathologist, 4, (2015). Available at: bit.ly/1ALR2Fg.
- HU Ahmed et al., “Diagnostic accuracy of multi-parametric MRI and TRUS biopsy in prostate cancer (PROMIS): a paired validating confirmatory study”, Lancet, [Epub ahead of print] (2017). PMID: 28110982.
- A El-Shater-Bosaily et al., “PROMIS—Prostate MR imaging study: a paired validating cohort study evaluating the role of multi-parametric MRI in men with clinical suspicion of prostate cancer”, Contemp Clin Trials, 42, 26–40 (2015). PMID: 25749312.
- AR Rastinehad et al., “Comparison of multiparametric MRI scoring systems and the impact on cancer detection in patients undergoing MR US fusion guided prostate biopsies”, 10, e0143404 (2015). PMID: 26605548.
My fascination with science, gaming, and writing led to my studying biology at university, while simultaneously working as an online games journalist. After university, I travelled across Europe, working on a novel and developing a game, before finding my way to Texere. As Associate Editor, I’m evolving my loves of science and writing, while continuing to pursue my passion for gaming and creative writing in a personal capacity.