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Prostate MRI followed by selective biopsy detected as many clinically significant cancers as standard ultrasound-guided systematic biopsy and detected 50% fewer low-risk cancers, a large randomized trial showed.

Targeted biopsy with multiparametric MRI identified grade group (GG) ≥2 tumors in 35% of men as compared with 30% for systematic biopsy with transrectal ultrasound (TRUS) guidance. The proportion of GG1 tumors decreased from 22% with TRUS biopsy (Bx) to 10% with targeted MRI-guided biopsy. Almost 40% of men randomized to the MRI group had negative imaging results, allowing them to avoid biopsy altogether.

Men who had MRI-guided prostate biopsy also had fewer adverse events (AEs), Laurence Klotz, MD, of the Sunnybrook Health Sciences Center in Toronto, and coauthors reported in .

"This study met its primary endpoint, demonstrating the noninferiority of MRI-TB [targeted biopsy] to conventional systematic biopsy based on the ITT [intention-to-treat] population," the authors stated. "In those who underwent biopsy, targeted biopsy was superior to systematic biopsy for the detection of GG2 or greater cancer. Therefore the strategy of MRI before biopsy appears to be superior to systematic TRUSBx."

Results of the study, known as , mirrored those of the previously reported PRECISION trial, which showed a 12% absolute difference in detection of clinically significant prostate cancer in favor of MRI-TB. In PRECISION, 28% of patients randomized to MRI-TB had negative imaging studies and avoided prostate biopsy.

Search for 'Ideal Pathway' Not Over

Despite the advantages demonstrated by PRECISE and PRECISION, the "ideal diagnostic pathway" for prostate cancer biopsy remains to be determined, according to the author of an .

"It is unlikely that it will be a strict combined pathway in which all patients would undergo MRI and then, systematically, combined systematic biopsy or targeted biopsy," wrote Olivier Rouvière, MD, PhD, Hôpital Edouard-Herriot and the University of Lyon in France. "It will probably not be a strict MRI pathway either, in which MRI alone would be used as a triage test for biopsy."

"More likely, MRI findings will be used in conjunction with other biomarkers such as PSA density to select, among the patients with positive MRI findings, those who need targeted biopsy (and those who may safely avoid it), and among the patients with negative MRI findings, those who may still deserve systematic biopsy."

Multiparametric MRI, with diffusion-weighted imaging and dynamic contrast enhancement, offers "additional conspicuity of cancer" to improve diagnostic accuracy, Klotz and coauthors said in the introduction to the PRECISE trial findings. Studies comparing the correlation between MRI and prostatectomy specimens for detection of prostate tumors larger than 0.5 mL -- clinically significant tumors -- showed sensitivity values of 40-77% and sensitivity of 81-95%.

The superior cancer detection capability of MRI afforded the opportunity to challenge the decades-long standard of TRUS-guided biopsy in men with suspected prostate cancer, the authors continued. TRUS is used primarily for anatomic guidance, and traditional ultrasonography poorly discriminates between benign and malignant tissue.

Multiple high-quality studies, in addition to PRECISION, showed promising results for MRI-TB. Nonetheless, MRI before biopsy has yet to become routine practice in many parts of the world, the authors noted.

The PRECISE and PRECISION trials had similar designs but with some notable differences, including risk-based eligibility criteria, systemic follow-up of all patients for 2 years (including repeat MRI in untreated patients), investigation of biomarkers in tissue and fluid, and an economic analysis.

PRECISE Design, Key Results

Investigators in PRECISE compared systematic 12-core TRUS-guided biopsy and MRI followed by targeted biopsy in 553 men with suspected prostate cancer and no prior prostate biopsy. Eligibility criteria included a ≥5% likelihood of prostate cancer, as determined by the . The primary outcome was the proportion of men with GG≥2 prostate cancer. In the MRI arm, patients underwent prostate biopsy only if the imaging study resulted in a PI-RADS score ≥3.

The results showed that 138 of 221 (62.4%) protocol-evaluable men underwent biopsy after MRI, and the remaining 37.6% avoided biopsy. By ITT analysis, GG≥2 prostate cancer was identified in 79 of 227 (35%) men in the MRI-TB arm and 67 of 225 (30%) in the TRUSBx arm. The frequency of GG1 prostate cancer was 10% with MRI-TB and 22% with TRUSBx.

A per-protocol analysis yielded similar results: GG≥2 prostate cancer in 36.1% of the MRI-TB arm and 33.2% of the TRUSBx arm.

MRI-TB was associated with a 24% absolute reduction in the incidence of adverse events (40% vs 64%), including hematospermia (22% vs 42%), hematuria (19% vs 48%), and pain (15% vs 32%). Erectile dysfunction occurred in 4% of men in each arm and urinary incontinence in 2% of the MRI-TB arm versus 5% of the TRUSBx group.

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