Chicago—A pivotal phase II trial of a novel MRI-guided ultrasound ablation treatment exceeded its primary efficacy endpoint of PSA decline in men with organ-confined prostate cancer.
In the prospective, open-label study of MRI-guided transurethral ultrasound whole-gland ablation (TULSA-PRO), 96% of men had a PSA decrease of at least 75% at 1 year. Approximately 80% of the men who entered the study with Gleason grade group 2 (Gleason score 7) prostate cancer no longer had evidence of Gleason grade group 2 disease at 1 year. Nearly two-thirds of men had a complete histologic response based on biopsy, principal investigator Scott Eggener, MD, reported at the AUA annual meeting in Chicago.
Rates of severe treatment-related toxicity were low, said Dr. Eggener, director of the Prostate Cancer Program at the University of Chicago.
The phase II study, conducted at 13 centers in the United States, Canada, and Europe, included 115 men with a median age of 65 years. Median pre-treatment PSA was 6.3 ng/mL and maximum PSA was 15.0 ng/mL. All men had Gleason grade group 2 or lower prostate cancer. Two-thirds of study participants had intermediate-risk disease, and the remainder had low-risk disease. More than 80% of men had Gleason grade group 2 or high-volume Gleason grade group 1 cancer, which is generally considered to be clinically meaningful disease, Dr. Eggener noted.
The intent of treatment was whole-gland ablation with sparing of the urethra and urinary sphincter. The procedure is performed entirely within the MRI suite under general anesthesia to eliminate motion. An ultrasound device, placed transurethrally under MRI guidance, continuously rotates and robotically delivers ultrasound waves peripherally to a predetermined contour around the prostate. Colorimetric feedback indicates when the target temperature of approximately 57 degrees Celsius is reached.
Following treatment, an MRI is provided to confirm the ablation margin. A suprapubic tube is placed for 2 weeks.
The procedure is capable of treating all sizes of prostates, Dr. Eggener said. It is not a form of high-intensity focused ultrasound, which is performed transrectally and has a different mechanism of applying ultrasound energy, he pointed out.
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