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CHICAGO -- MRI-guided ultrasound ablation of the prostate met a PSA-defined endpoint in 96% of men with newly diagnosed localized prostate cancer, according to a study reported here.

Overall, 110 of 115 men had ≥75% reduction in baseline PSA value 1 year after transurethral ultrasound ablation (TULSA). Among men with clinically significant prostate cancer (), 79% did not have clinically significant disease after the treatment.

Follow-up MRI at 12 months showed a 90% reduction in median prostate volume, reported Scott Eggener, MD, of the University of Chicago, at the (AUA) annual meeting.

"The data are encouraging, but it's still only one year [of] follow-up," Eggener told MedPage Today. "It appears to be relatively safe, but not entirely risk free. It certainly accomplished the goal of reducing the size of the prostate. The biopsy outcomes were overall favorable, but not uniformly so."

Follow-up in the cohort will continue for 5 years, as some European investigators continue their investigation of the treatment effects, he added. Discussions have begun with the FDA about potential approval for ablation of prostate tissue.

Despite the near-universal achievement of the PSA goal, a substantial number of men still had Gleason group 2 disease after treatment, noted Alexander Kutikov, MD, of Fox Chase Cancer Center in Philadelphia.

"This is preliminary data with an emerging technology," said Kutikov. "I would caution against judging the success on the basis of PSA response, which is not an established metric of treatment response. The prostate volume reduction could explain the PSA response. That does not mean that the cancer was addressed."

The side effect profile "was not terrible," he added, but "it's clear you're exposing patients to the risk of certain side effects."

How It Works

Performed with MRI guidance and general anesthesia, TULSA employs a transurethral device that continuously rotates and emits thermally ablative ultrasound waves around the prostate. MRI provides the basis for developing individualized treatment algorithms implemented by means of automated robotic delivery.

The system has continuous temperature measurement and automated energy adjustment to maintain a predefined temperature in the prostate and urethra, said Eggener. The procedure does not transmit energy through the rectum, and the system can be used to treat prostates of any size, ablating 1-2 cc of tissue per minute.

Investigators at 13 centers in 5 countries enrolled patients in the study. Eligible patients had baseline PSA levels ≤15 ng/mL and were Gleason grade ≤3 + 4 (defined as Gleason Grade Group 1-2). Two-thirds of the men had intermediate-risk prostate cancer and the rest had low-risk disease. The primary endpoints, assessed at 12 months, were safety and efficacy, the latter defined as a PSA reduction ≥75% from baseline in >50% of patients.

The PSA reduction goal was met in 96% of the patients, who had a median PSA reduction of 95%. The cohort had a median PSA nadir of 0.34 ng/mL, and the median perfused prostate volume decreased from 41 cc at baseline to 4 cc at 12 months.

Investigators performed 10-core prostate biopsies with high-density sampling at baseline and 12 months. Among the 68 men with clinically significant prostate cancer (Gleason group 2), 54 (79%) did not have clinically significant disease at 12 months. Two-thirds of 111 evaluable patients had complete histologic response to treatment (no evidence of disease). Of 39 positive biopsies, 16 were found to have clinically insignificant disease (very low risk).

Adverse Events

Eggener reported a 7% incidence of serious adverse events (SAEs), the most common being genitourinary infection (4.3%). Remaining SAEs consisted of one case each of urinary retention, urinoma, ileus, deep-vein thrombosis, urethral stricture, and urethral calculus.

By surgeon assessment, 2.6% of patients had moderate urinary incontinence (Grade 2, absorbent pads indicated) at 1 year. Patient-reported outcomes (PROs) showed that 7% of the men wore a security pad, but fewer than 1% reported being incontinent (using more than one pad per day). PRO data also showed a 3.8% increase in the proportion of men with daily urine leakage 1 year after their TULSA procedures.

With regard to erectile function, three-fourths of the men reported having erections sufficient for penetration at the 12-month follow-up. No patient had severe erectile dysfunction.

Eggener said a multivariate analysis identified three factors associated with an increased likelihood of clinically significant prostate cancer at follow-up: intraprostatic calcification at screening, complex data related to thermal coverage during treatment, and presence of a ≥3 lesion by .

The early results are encouraging, but more experience and longer follow-up are needed to know whether TULSA will distinguish itself from other alternatives to surgery and radiation for localized prostate cancer, said Douglas Dahl, MD, of Massachusetts General Hospital in Boston.

"It appears to fall into the category of 'other technologies,' like HIFU (high-intensity focused ultrasound) and cryoablation, where we're looking for a minimally invasive treatment to manage early-stage prostate cancer and try to minimize the side effects," said Dahl. "Treatment without having to go through the rectum is appealing as compared with a transrectal approach, and they didn't report any rectal injuries."

"The big concern with all of these technologies is that, when you rebiopsy the prostate, you still find a significant percentage of patients who have some detectable prostate cancer within the first 6 months to a year," he added. "The key thing will be the long-term cancer outcomes, to find out whether this is really effective. We need a lot more long-term data before it can become a standard part of treatment."

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