MRI-Targeted Biopsy May Be Of Added Value In Prostate-Cancer Detection

Magnetic resonance imaging (MRI) with targeted biopsy (TB) is not inferior to systematic 12-core transrectal ultrasonography (TRUS) biopsy for diagnosing prostate cancer, and may have advantages, according to the results of a randomized trial.

"These findings show decisively that MRI together with targeted biopsies offer patients a less invasive procedure, the chance to avoid a biopsy all together and can help avoid the over-treatment of clinically insignificant prostate cancer - all while detecting a higher rate of clinically significant cancers," Dr. Laurence Klotz of Sunnybrook Health Sciences Centre, in Toronto, told Reuters Health by email.

TRUS biopsy has been used for more than three decades to diagnose prostate cancer in patients with elevated prostate-specific antigen (PSA) levels, Dr. Klotz and colleagues note in JAMA Oncology.

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Although MRI is more sensitive for higher-grade cancers, say the researchers, the evidence is less clear in active surveillance. "There is an unmet need for a test that identifies clinically significant prostate cancer without overdiagnosing insignificant cancer," they add.

To investigate, the team randomized 453 patients to undergo TRUS biopsy or MRI-TB. Results were evaluable for 421 patients. A lesion with a Prostate Imaging Reporting and Data System version 2 score of 3 or greater was detected in 62.4% of the MRI group, and 83 of these men (37%) had a negative MRI result and avoided biopsy.

Cancers of International Society of Urological Pathology grade group (GG) 2 or greater were identified in 30% of the men who underwent TRUS biopsy versus 35% allocated to MRI-TB.

"MRI with targeted biopsy found five [percentage points] more clinically significant prostate cancers compared to those receiving systematic TRUS-TB biopsies, conclusively demonstrating the method matches the performance of the current standard of care," Dr. Klotz said

In addition, he said, "More than a third of patients in the MRI arm of the trial avoided biopsies altogether following negative imaging results. Those individuals received a follow-up MRI in two years' time."

Meanwhile, "Use of MRI reduced the unnecessary diagnosis of slow-growing, clinically insignificant prostate cancers by 55% (from 22% to 10%)," Dr. Klotz added.

"Those who did have biopsies in the MRI arm had significantly fewer samples taken when compared to systematic TRUS-TB, resulting in less pain and discomfort for patients," he concluded. "Moreover, the MRI arm had a decreased adverse event profile, including less hematuria and incontinence."

In an accompanying editorial, Dr. Olivier Rouviere of the University of Lyon, in France, predicts that ultimately, "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."

"Another interesting aspect of the study," he told Reuters Health by email, "is the intersite analysis. It showed major variability among participating centers in clinically significant prostate cancer detection rates yielded by targeted and systematic biopsy. This underlines the absolute need for quality control for all the steps of the diagnostic pathway of prostate cancer."

—David Douglas

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