Is Focal Therapy With MRI-Guided Focused Ultrasound Safe and Effective for Grade Group 2 or 3 Prostate Cancer?

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In a phase IIb study reported in The Lancet Oncology, Ehdaie et al found that focal ablation with magnetic resonance imaging (MRI)-guided focused ultrasound successfully treated a high proportion of patients with grade group 2 or 3 prostate cancer.

As stated by the investigators, “Men with grade group 2 or 3 prostate cancer are often considered ineligible for active surveillance; some patients with grade group 2 prostate cancer who are managed with active surveillance will have early disease progression requiring radical therapy.”

Study Details

A total of 101 patients with intermediate-risk, previously untreated disease (prostate-specific antigen ≤ 20 ng/mL, grade group 2 or 3; tumor classification ≤ T2) were enrolled in the U.S. multicenter trial between May 2017 and December 2018. MRI-guided focused ultrasound energy sequentially titrated to temperatures sufficient for tissue ablation (approximately 60°C–70°C) was delivered to the index lesion and a planned margin of ≥ 5 mm of normal tissue using real-time magnetic resonance thermometry for intraoperative monitoring. The primary efficacy outcome was absence of grade group 2 and higher disease in the treated area at 6-month and 24-month intervals on combined MRI-guided and systematic biopsy.  

Key Findings

Overall, 96 (95%, 95% confidence interval [CI] = 89%–98%) of 101 patients had no evidence of grade group 2 or higher prostate cancer in the treated area at 6 months. At 24 months, 78 (88%, 95% CI = 79%–94%) of 89 patients had no evidence of grade group 2 or higher cancer in the treated area. Among the 11 men with grade group 2 or higher cancer in the treatment area at 24 months, 3 had grade group 4 or higher disease.

No evidence of grade group 2 or higher cancer was detected anywhere in the prostate in 77 (76%, 95% CI = 67%–84%) of 101 patients at 6 months or in 59 (60%, 95% CI = 50%–70%) of 98 patients at 24 months. At 6 months, 19 patients (19%) had newly detected grade group 2 or higher cancer exclusively outside of the treatment area.

A single grade 3 treatment-related adverse event (urinary tract infection) was reported; no grade 4 treatment-related adverse events or treatment-related deaths were reported. Common grade ≤ 2 treatment-related adverse events were hematuria (24%) and urinary retention (15%). A total of 18% of patients reported grade 2 or lower urinary incontinence; however, no patient reported stress urinary incontinence requiring pad use throughout the study period.

The investigators concluded, “24-month biopsy outcomes show that MRI-guided focused ultrasound focal therapy is safe and effectively treats grade group 2 or 3 prostate cancer. These results support focal therapy for select patients and its use in comparative trials to determine if a tissue-preserving approach is effective in delaying or eliminating the need for radical whole-gland treatment in the long term.”

Behfar Ehdaie, MD, of the Urology Service, Department of Surgery, Memorial Sloan Kettering Cancer Center, is the corresponding author for The Lancet Oncology article.

Disclosure: The study was funded by the National Cancer Institute and Insightec. For full disclosures of the study authors, visit

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