MRI-targeted biopsy is superior to standard biopsy for prostate cancer diagnosis

Robyn Boyle, RPh, for MDLinx | April 17, 2018

An international, multi-center study reported that magnetic resonance imaging (MRI) and MRI-targeted biopsy, if needed, were superior to standard transrectal ultrasonography-guided biopsy in men at clinical risk for prostate cancer. The results were published in the New England Journal of Medicine.

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Clinically significant cancer was detected in 38% of men in the MRI-targeted biopsy group and in 26% of men in the standard-biopsy group.

Men with an elevated prostate-specific antigen (PSA) level or an abnormal digital rectal examination are typically offered a standard transrectal ultrasonography-guided biopsy of the prostate, during which 10 to 12 cores are obtained. This approach is associated with the underdetection of clinically significant prostate cancers and the overdetection of clinically insignificant cancers.

Veeru Kasivisvanathan, MBBS, BSc, MRCS, MSc, from the University College London, led the study, which compared MRI-targeted biopsy with standard transrectal ultrasonography-guided biopsy in a randomized trial. The investigators found that “MRI with or without targeted biopsy was conclusively superior to standard transrectal ultrasonography-guided biopsy.”

Men with a clinical suspicion of prostate cancer were randomly assigned to undergo MRI or standard transrectal ultrasonography-guided biopsy. If the MRI was suggestive of prostate cancer, the participants underwent MRI-targeted biopsy with the use of real-time ultrasonographic guidance. A biopsy was not offered if MRI results were not suggestive of prostate cancer.

In addition, participants reported intervention-specific side effects immediately, and at 30 days after their procedure. Health-related quality of life (QoL) was assessed with the use of the EuroQol-5 Dimension Self-Report Questionnaire at baseline, 24 hours after the intervention, and 30 days after the intervention.

The primary outcome was the proportion of men with clinically significant cancer, defined as the presence of a single biopsy core indicating disease of Gleason score 3+4 (Gleason sum of 7).

Secondary outcomes included the proportion of men with clinically insignificant cancer (Gleason score 3+3), the proportion of men in the MRI-targeted biopsy group who did not undergo biopsy, and adverse events after the intervention.

Participants were followed until treatment decisions were made, or until 30-day post intervention questionnaires were completed. If further diagnostic tests were needed, followed-up continued until after the results were available. Participants who had negative test results in either group returned to standard-care monitoring at each center, which typically involved surveillance of the PSA level.

A total of 500 participants underwent randomization at 23 international sites; 252 participants were assigned to the MRI-targeted biopsy group and 248 to the standard-biopsy group.

Among the participants assigned to the MRI-targeted biopsy group, 28% had results not suggestive of prostate cancer, and did not undergo biopsy.

A median of 4 biopsy cores were obtained in the MRI-targeted biopsy group, compared with a median of 12 cores in the standard-biopsy group.

Clinically significant cancer was detected in 95 men (38%) in the MRI-targeted biopsy group and in 64 men (26%) in the standard-biopsy group (95% confidence interval [CI]; P=0.005). The authors explained that the 95% CI showed the superiority of MRI, with or without targeted biopsy, over transrectal ultrasonography-guided biopsy. The results were consistent in the modified intention-to-treat and per-protocol populations.

Fewer participants received a diagnosis of clinically insignificant cancer in the MRI-targeted biopsy group than in the standard-biopsy group (9% vs 22%; P < 0.001).

Health-related QoL at 24 hours and at 30 days after the intervention did not differ significantly between groups.

The participant-reported complications at 30 days were less frequent in the MRI-targeted biopsy group than in the standard-biopsy group, including events of blood in the urine (30% vs 63%), blood in the semen (32% vs 60%), pain at the site of the procedure (13% vs 23%), rectal bleeding (14% vs 22%), and erectile dysfunction (11% vs 16%). The authors suggested that this reflects the lower percentage of men undergoing biopsy and fewer biopsy cores obtained in the MRI-targeted biopsy group than in the standard-biopsy group.

More men in the standard-biopsy group than in the MRI-targeted biopsy group underwent further diagnostic tests (16% vs 3%), and more men in the MRI-targeted biopsy group adopted a strategy of monitoring the PSA level (41% vs 30%).

The authors admit that the study had some limitations. The central quality-control review of MRI showed only moderate agreement (78%) between the site and the central radiologist reading, which they feel highlights the need for further improvements to the standardization, reproducibility, and reporting of multiparametric MRI.

In addition, some of the pathological test results were upgraded or downgraded on central pathological review, although the differences were not substantial between groups. There are also concerns about the men with negative results on MRI who do not undergo biopsy. It is possible that clinically significant cancers may have been missed by not doing standard biopsy in men in the MRI-targeted biopsy group.

The investigators acknowledge that there will be a learning curve for performing MRI of the prostate; they suggest supervision by an experienced radiologist. Furthermore, changes in the standard of care for diagnosis of prostate cancer would require health care systems to adapt to accommodate appropriate MRI capacity and to meet the training needs of radiologists and urologists.

Although that would be expensive, the changes may be cost-effective in the long term with earlier detection of clinically significant cancers, fewer cases of insignificant cancer diagnosed, and fewer repeat biopsies.

“In men with a clinical suspicion of prostate cancer, we found that a diagnostic pathway including risk assessment with MRI before biopsy and MRI-targeted biopsy in the presence of a lesion suggestive of cancer was superior to the diagnostic pathway of standard transrectal ultrasonography-guided biopsy,” the authors concluded.

To read more about this study, click here

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