MR-Guided Biopsy of the Prostate Trumps Transrectal Approach

Pam Harrison

March 11, 2013

VIENNA, Austria — Magnetic resonance (MR)-guided biopsy of the prostate is a safe and effective alternative to the standard transrectal ultrasound-guided biopsy, and patients prefer it, according to 2 new studies.

"The problem with the transrectal approach is that significant cancers are missed, insignificant cancers are detected by chance, and there's a high percentage of undergrading of the lesions," lead researcher of one of the studies, Stephan Polanec, MD, from the Medical University of Vienna in Austria, told Medscape Medical News.

"MR-guided biopsy is a targeted biopsy with pinpoint accuracy and a higher detection rate. It also detects cancer in the anterior part of the prostate, which the transrectal approach isn't able to do," he explained here at the European Congress of Radiology 2013.

In the first study, Dr. Polanec and colleagues analyzed 44 biopsies from 41 patients that were initially identified as suspicious on multiparametric magnetic resonance imaging (MRI), which combines several different MRI techniques to render a complex image of the prostate.

Mean patient age was 65 years and mean prostate-specific antigen (PSA) level was 8.17 ng/mL. All patients had at least 1 previous negative transrectal ultrasound-guided biopsy.

Dr. Polanec explained that for MR-guided biopsy, patients are placed in the prone position with the head forward and an 18-gauge needle is inserted transrectally. Approximately 3 or 4 biopsy cores are extracted during the procedure.

MR-guided biopsy is a targeted biopsy with pinpoint accuracy and a higher detection rate.

On MR-guided biopsy, conducted in a 1.5 Tesla MR unit, lesions were identified as malignant in 11 patients. In the remaining 30 patients, no prostate cancer was detected on MR-guided biopsy and no prostate cancer was subsequently identified during active monitoring (mean follow-up, 36 months).

Of the 11 patients in whom prostate cancer was identified, 5 had a Gleason score of 6, 4 had a Gleason score of 7, 1 had a Gleason score of 8, and 1 had a Gleason score of 9.

In 9 patients, the cancer was identified in the peripheral zone of the prostate, in 1 patient it was in the transition zone, and in 1 it was in the central zone.

"It's very important to mention that no new prostate cancer was detected during our follow-up of the benign lesions, so the sensitivity of MR-guided biopsy was therefore 100%," Dr. Polanec said.

"While I don't think MR-guided biopsy will replace the transrectal approach, if I were a patient, I would prefer doing the multiparametric MRI in combination with MR-guided biopsy because you reduce the number of cores you need and it's just more comfortable," he said.

More Comfortable for Patients

In the second study, lead researcher Tobias Franiel, MD, from Charité Medical University in Berlin, Germany, and colleagues compared acceptance, adverse effects, and complications between MR-guided biopsy and transrectal ultrasound-guided biopsy.

The researchers looked at 54 patients with a median PSA of 12.1 ng/mL. All patients had at least 1 previous negative result on transrectal ultrasound-guided biopsy, during which 10 to 12 biopsy cores were harvested.

Patients subsequently underwent MR-guided biopsy, and were then questioned about pain duration and intensity, adverse events, and their preferred procedure.

"Sixty-five percent of patients indicated they preferred the MR-guided biopsy because there were fewer side effects and they expected better results than with the transrectal approach," Dr. Franiel explained.

Patients rated pain duration and intensity significantly lower with MR-guided biopsy, and 82% said they would prefer the MR-guided approach for any subsequent biopsies.

Both approaches had a low complication rate (6% each).

However, "our study had several limitations," Dr. Franiel acknowledged.

First, the median interval between the initial procedure and subsequent MR-guided biopsy was 13 months, which is admittedly "quite long," he said.

Second, patients were questioned only after the MR-guided biopsy, not after the transrectal approach.

It is quite possible that these 2 issues could "have led to a recall bias," he pointed out.

In addition, because all patients had at least 1 negative ultrasound biopsy, it could be that they were negatively biased against that approach and favorably predisposed to think positively about MR-guided biopsy.

"Nevertheless, we think it's justified to conclude that patients prefer targeted MR-guided biopsy of the prostate...due to lower pain intensity and fewer side effects, Dr. Franiel said. "Targeted MR-guided biopsy is a suitable option for patients with persistent suspicion of prostate cancer," he added.

Jurgen Fütterer, MD, from Radboud University Nijmegen Medical Centre in the Netherlands, who was asked by Medscape Medical News to comment on these studies, agrees that ultrasound-guided biopsy has a poor yield for cancer detection (range, ~40% to 45%).

He also agrees that the multiparametric MR-guided approach is a far more targeted option and requires far fewer biopsies for histopathologic analysis.

"With the MR-guided technique, you use imaging to guide the needle to the exact spot identified on multiparametric MRI, so you need far fewer biopsies and you are sure you're right on target," Dr. Fütterer said.

In addition, in patients with a negative biopsy, the likelihood of picking up a subsequent cancer on an additional ultrasound biopsy is only about 12% to 14%.

The detection rate found by Dr. Polanec's team was approximately 27%, which is low compared with the reported 40% to 50% detection rate for MR-guided biopsy in patients with negative ultrasound-guided biopsy results, but better than an additional ultrasound biopsy would have yielded, Dr. Fütterer noted.

Dr. Polanec, Dr. Franiel, and Dr. Fütterer have disclosed no relevant financial relationships.

European Congress of Radiology (ECR) 2013: Abstracts B171 and B172. Presented March 7, 2013.