MR-Guided Laser Ablation of Prostate Cancer Producing Promising Results

Rosemary Frei, MSc

September 2013, Vol 4, No 7 - Prostate Cancer

Niagara Falls, Ontario—Magnetic resonance (MR) imaging or MR-guided laser focal therapy for ablating low- to intermediate-risk prostate tumors is showing promise in the hands of a Toronto team, despite a relatively high failure rate.

In a series of 40 patients, 37 of whom were biopsied 4 months after MR-guided laser focal therapy ablation, 21 (48%) of the men had completely negative biopsies; 8 had negative biopsies in the ablated area but positive in a different area of the prostate, including 5 in a contralateral lobe. The remaining 11 patients were positive in the ablated area.

Uri Lindner, MD, a Urologic Oncol­ogy Fellow, Department of Surgical Oncology, University Health Network, Toronto, Canada, presented the results at the 2013 Canadian Urological Association annual meeting.

“This will change the way we treat prostate cancer in a parallel way to how colonoscopy changed the treatment of colorectal cancer: with colonoscopy, if you see a polyp, you just snare and remove it, and if you don’t get it all, so what? You have the patient come back in 4 months and do it again,” said Dr Lindner.
The 40 patients underwent 42 procedures (all as outpatients) and were followed for an average of 710 days. The men’s mean baseline prostate-specific antigen level was 5.3 ng/mL. The average tumor volume was 1.0 g and the average volume of ablated tissue was 8.8 g.

No intraprocedure complications were seen and 3 postprocedure urinary infections resolved within 1 week. One man with an apical tumor had stress incontinence for 6 weeks postprocedure, which resolved without intervention.

Of the 11 men who failed treatment, 5 received a radical prostatectomy or radiotherapy, and the other 6 remain on active surveillance.
This procedure has a 100% cancer-specific survival and overall survival rate, said Dr Lindner.

Overall, 31 of the 33 patients with mild or no erectile dysfunction (ED) before the procedure were still potent after the procedure, without using ED medication. Two men who had mild ED before the procedure needed low-dose phosphodiesterase type 5 inhibitors to maintain erections sufficient for intercourse.

Dr Lindner stated that the team members are continuing to improve their success rate, but the approach is technically challenging. “The MR is not able to delineate all the tumor, so if you ablate only the MR target, you’re still going to get a positive biopsy on the rim of the ablation [zone]….And it’s not very easy in the MR environment to place the needle exactly where you want,” he said. But ablating the rim beyond the targeted area should be able to get all or most of the tumor.

Dr Lindner defended this approach by saying that in approximately 94% of patients who had an MR-visualized tumor and underwent prostatectomy, the index lesion was the one that was detected by the MR. “And you might find minute cancers somewhere else, but…by ablating the [index] area, you’re probably preventing extracapsular extension and perhaps metastatic disease,” he told the audience.