Using multi-parametric magnetic resonance imaging to triage men with high serum PSA could save about one-fourth of patients from having transrectal ultrasound-guided prostate biopsy, according to a recent study.
Using multiparametric magnetic resonance imaging (mpMRI) to triage men with high serum PSA could save 27% of patients from having transrectal ultrasound-guided prostate biopsy (TRUS biopsy), according to a new study published online in The Lancet (Jan. 19, 2017).
Doing the scan prior to biopsy could also improve the diagnosis, reducing the detection of clinically insignificant cancers by 5%, while improving detection of clinically significant disease, the authors wrote.
“We must seriously consider changing our practice across all health care settings to institute an imaging test-multiparametric MRI, in this instance-before a biopsy test, which is random. 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,” said lead author Hashim U. Ahmed, PhD, BM, BCh, of Imperial College, London.
The study helps to create a level of evidence that was lacking in the use of mpMRI in diagnosing prostate cancer. Many papers were retrospective; many compared mpMRI to surgical specimens, which meant that all men had to have cancer on biopsy and then choose surgery. Still others compared mpMRI to TRUS-biopsy, which is known to be inaccurate, and many studies were based in centers of excellence, according to Dr. Ahmed.
“As a result of these methodological biases, there was considerable uncertainty and skepticism about the performance of mpMRI,” Dr. Ahmed said.
In this study, 576 men with PSA concentrations up to 15 ng/mL and no prior biopsies were given an mpMRI. The mpMRI looks at tissue anatomy, as well as prostate volume, cellularity, and vascularity. There is evidence that this scan type is likely to detect higher risk disease and overlook low-risk disease, according to the study.
Patients in the multicenter study also received a TRUS biopsy and template prostate mapping biopsy as a reference test.
The authors defined clinically significant prostate cancer as having a Gleason score of ≥4+3 or a cancer core length of 6 mm or longer of any grade.
The results: TPM biopsy found 40% of subjects had aggressive cancer. Of these, the mpMRI correctly diagnosed 93% of aggressive cancers, compared to TRUS biopsy, which correctly diagnosed 48%. Among the men with a negative mpMRI scan, 89% had clinically insignificant cancer or no cancer.
Dr. Ahmed said that before this study, he and colleagues had conducted a number of studies comparing mpMRI to template mapping biopsies, which sample the entire prostate every 5 mm throughout the prostate and can be used in almost all men, thereby reducing selection bias.
“All of our studies and other groups’ research showed that mpMRI had excellent performance characteristics, but further evidence was needed. Patients, clinicians, and hospitals now have level 1 evidence to demonstrate that having an mpMRI before a first biopsy improves their chance of finding significant cancer that would otherwise be missed by a transrectal biopsy. For those wishing to avoid a first biopsy, an mpMRI beforehand can rule out significant disease with a high degree of probability, and men could safely enter clinical and serum PSA monitoring, rather than immediate biopsy. Some of these men might in time need a biopsy to overcome the false-negative rate of mpMRI,” Dr. Ahmed said.
The trick will be to ensure that clinicians are using and have access to the appropriate equipment, according to Dr. Ahmed.
“First, do we have capacity for these scans on existing scanners? Second, the mpMRI scans need to be optimized to meet international standards. Third, there exists limited radiological expertise for reporting these scans and, therefore, radiologists with an interest in this area need to consider training programs and courses, as well as buddying up together to learn from others’ experience,” he said.
More research is needed to evaluate targeting with MRI. There are different ways of deploying the needle to suspicious areas. For example, the operator might estimate a lesion’s location or use devices that fuse the MRI with ultrasound. Some do the biopsies inside the MRI scanner itself.
“The detection rates and cost-effectiveness of these various approaches require further work,” Dr. Ahmed said. “Further work is also needed to see if liquid biomarkers might help identify men at risk before having an mpMRI, in order to reduce the costs and capacity issues that many health care settings will have about MP-MRI.”
There might be other ways to use the MRI in prostate cancer. Dr. Ahmed is starting a study on using mpMRI as a screening tool instead of PSA blood testing in high-risk men, such as African-American men or men with a family history.
Dr. Ahmed receives funding to conduct trials from Sophiris, Trod Medical, and Sonacare. He receives payments for lectures and training from Sophiris, Sonacare, and Galil Medical.
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