MR-Guided Cryoablation in Recurrent Prostate Cancer

Becky McCall

February 27, 2012

February 27, 2012 (Paris, France) — Transperineal magnetic resonance (MR)-guided focal cryoablation has been shown to be feasible and safe in patients with prostate cancer who have experienced a recurrence after radiotherapy ablation.

To date, focal cryoablation has been conducted using transrectal ultrasound (TRUS) guidance.

"TRUS-guided procedures are not accurate enough to allow focal therapy. Until now, clinicians have tended to ablate the whole prostate because the focus is not very visible with TRUS," explained principal investigator Jelle Barentsz, MD, from the Department of Radiology, Radboud University Nijmegen Medical Center, the Netherlands.

"The initial results are very good," Dr. Barentsz announced.

He presented the work on behalf of his coauthors — Jurgen Fütterer, MD; Derya Yakar, MD; and Joyce Bomers, MSc — here at the European Association of Urology 27th Annual Congress.

In an interview with Medscape Medical News, Dr. Barentsz clearly stated that MR-guided focal cryoablation is "a major step forward. First, with multiparametric MR imaging (MP MRI), the tumor is more visible. Second, you can place a needle under MR image guidance in the most aggressive part of the tumor. Third, you can treat it better using the same technique."

Given this clarity of vision with MP MRI, the next logical step was to use it during focal cryoablation. "We want to kill as much as necessary but preserve normal healthy tissue as much as possible. We need to minimize damage and side effects, such as rectal fistulae, erectile dysfunction, and incontinence."

"We use an ice ball at -40 °C, which will kill. With 2 to 4 needles, you can carefully shape the ice ball to the area of tumor you wish to kill."

Cryoablation takes around 2.5 hours, and the patient is under general anesthesia. The patient is in the hospital for 2 days.

Currently, this procedure has only been carried out in a small number of patients who had a recurrence of prostate cancer after radiation therapy, but the results represent a step change in treatment options for these patients, for whom there are few alternative procedures. According to Dr. Barentsz, surgery is too difficult because of fibrosis of the tumor after radiotherapy, and hormonal treatment is only palliative, has significant adverse effects, and is expensive.

Nine patients received MR-guided focal cryoablation of the prostate. Seven of the 9 went home the day after the procedure. The other 2 went home 1 day later. To date, 5 patients have been followed for 3 months. Prostate-specific antigen (PSA) levels have dropped considerably in 4 of the 5 patients.

"This achieves local tumor control," said Dr. Barentsz. "Maybe it's not a cure, but for a very aggressive disease that can kill, it is now more like a chronic disease, at the cost of only 2 days of hospitalization."

Furthermore, he noted that the procedure does not require an ultrasound probe in the rectum, but rather a balloon with warm water. "This technique better preserves the rectal wall, which is difficult with the ultrasound approach. I predict this technique will have a lower incidence of painful rectal fistulae. It may even protect the neurovascular bundle, which is also in that area."

Dr. Barentsz conceded that before any conclusions can be drawn, larger trials with longer follow-ups are needed. The researchers hope to progress to using 3 Tesla MRI, which has a stronger magnetic field with higher resolution, allowing greater control of the ice ball.

Commenting on the work, Damian Greene, MB, MCh, FRCSI, FRCS (urol), from Sunderland Royal Hospital, United Kingdom, who presented a study on cryotherapy in low-risk disease in the same session, said focal cryotherapy is still evolving.

"Most urologists use transperineal template mapping biopsies to stage the cancer or to exclude any areas that are not being treated. In the future, it would be very exciting [if MRI is proven] good enough to use in that way because it will save the patients an extra technique and it will make it easy to perform focal therapy."

Per-Anders Abrahamsson, MD, PhD, professor of urology at Lund University, Sweden, asked about the use of MRI by nonexperts. "You need to be an expert in MRI to use this in the diagnosis of prostate cancer, so do you really think all radiologists will use it this way?... In addition, do you think we urologists can learn to use these instruments to limit the number of biopsies? This is critical. If this is the future, then this will change our diagnostic armamentarium."

Dr. Barentsz stressed that radiologists need education in the technique so that they can combine their skills with urologists. "I think multidisciplinary collaboration in this respect is very important."

Dr. Barentsz said the work on MP MRI to guide focal cryoablation is supported by 2 recently published studies done by his group.

In one study, led by Caroline Hoeks, MD, 41% of patients with elevated PSA and 1 or more negative TRUS-guided biopsy were found to have prostate cancer on MP MRI-guided biopsy of suspicious regions. The majority of these (87%) were clinically significant (Eur Urol. 2012; published online ahead of print February 1, 2012).

According to Dr. Barentsz, the findings of that study gave a key message to urologists: "Whenever you have a negative TRUS biopsy, you need to conduct an MP MRI and then a more targeted biopsy. The study shows that by using MR-guided biopsy, you find tumors that would have otherwise been undetected in 41% of patients," he remarked.

In the second study (Eur Urol. 2012;61;177-184), a Dutch team, led by Thomas Hambrock, MD, compared tumor aggression using a Gleason score at prostatectomy with findings on biopsy. Patients in one group received TRUS-guided biopsies and in the other received an MP MRI and had MR-guided biopsies. All patients underwent prostatectomies to facilitate review of the usefulness of each approach.

Those researchers found that there was significant undergrading of Gleason grade 3 tumors with TRUS-guided biopsy. TRUS-guided biopsy had an underscoring of 44%, which was reduced to 5% for MR-guided biopsy.

They also found that MP MRI reveals the most severely affected areas of the tumor. "If a needle is targeted to this area, then MR images allow guidance to the most severely affected part of that tumor," Dr. Barentsz explained.

Dr. Barentsz reports receiving support from Galil Medical. Dr. Greene and Dr. Abrahamsson have disclosed no relevant financial relationships.

European Association of Urology (EAU) 27th Annual Congress. Presented February 24, 2012.

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