MP-MRI Could Help Avoid Unnecessary Prostate Biopsies

February 1, 2017

The use of multi-parametric magnetic resonance imaging could allow more than a quarter of men with high prostate-specific antigen levels to avoid undergoing transrectal ultrasound-guided prostate biopsy.

The use of multi-parametric magnetic resonance imaging (MP-MRI) could allow more than a quarter of men with high prostate-specific antigen (PSA) levels to avoid undergoing transrectal ultrasound-guided prostate biopsy (TRUS-biopsy), according to a new study. MP-MRI could also increase the number of clinically significant cancers discovered while avoiding overdiagnosis of insignificant disease.

The standard diagnostic pathway for prostate cancer involves TRUS-biopsy after an elevated PSA test. “As a result, many men without cancer undergo unnecessary biopsies, clinically insignificant cancers are often detected and clinically significant cancers are sometimes missed,” wrote study authors led by Hashim U. Ahmed, FRCS, of University College London. “TRUS-biopsy also carries significant morbidity and can cause life-threatening sepsis.”

The new study tested whether MP-MRI could help avoid some of those biopsies. Researchers enrolled 740 men with PSA levels up to 15 ng/mL with no previous biopsy; of those 576 underwent 1.5 tesla MP-MRI followed by both TRUS-biopsy and a reference test, template prostate mapping biopsy (TPM-biopsy). The results were published online ahead of print in Lancet.

TPM-biopsy revealed cancer in 408 men (71%); 230 men had clinically significant disease (40%). The sensitivity of MP-MRI for clinically significant cancer was 93%, with a negative predictive value of 89%. The specificity was 41%, and it had a positive predictive value of 51%. A total of 158 men had a negative MP-MRI, and 17 of those had clinically significant disease based on TPM-biopsy. There were 44 serious adverse events reported, including eight cases of sepsis.

MP-MRI had a higher sensitivity than TRUS-biopsy (93% vs 48%), with a McNemar test ratio of 0.52 (95% CI, 0.45–0.60), as well as a higher negative predictive value (89% vs 74%) with an odds ratio of 0.34 (95% CI, 0.21–0.55; P < .0001). TRUS-biopsy, meanwhile, had a better specificity (96% vs 41%), with a McNemar test ratio of 2.34 (95% CI, 2.08–2.68; P < .0001), and a better positive predictive value (90% vs 51%) with an odds ratio of 8.2 (95% CI, 4.7–14.3; P < .0001).

In a scenario where men first undergo MP-MRI and only those with a suspicious result undergo TRUS-biopsy, 158 of 576 men (27%) would have been able to avoid the biopsy. Also, up to 18% more cases of clinically significant prostate cancer might be detected, and 5% fewer insignificant tumors would be found.

“TRUS-biopsy performs poorly as a diagnostic test for clinically significant prostate cancer,” the authors concluded. “MP-MRI, used as a triage test before first prostate biopsy, could identify a quarter of men who might safely avoid an unnecessary biopsy and might improve the detection of clinically significant cancer.” They noted that a cost-effectiveness analysis of MP-MRI in this setting is underway, but that the primary outcome data provide a strong argument for the test’s use.