AUA 2021: MRI-guided Focused Ultrasound Focal Therapy for Intermediate-Risk Prostate Cancer: Final Results of a Phase IIb Multicenter Study 

(UroToday.com) The American Urologic Association (AUA) annual meeting included a late-breaking abstract session with a presentation by Dr. Behfar Ehdaie discussing results of a phase IIb multicenter study assessing MRI-guided focused ultrasound focal therapy for intermediate-risk prostate cancer. Radical whole-gland therapy for prostate cancer can lead to significant side effects, including a decline in erectile function and urinary continence. Patients with Grade Group 2 or 3 prostate cancer are often ineligible for active surveillance or experience early disease progression (40% within 5 years in ProtecT1) on active surveillance requiring radical therapy. Focal therapy has emerged as an alternative treatment with the goal to reduce side effects and maintain cancer control by targeting areas of known cancer with the prostate gland. Multicenter, retrospective studies have shown focal therapy for prostate cancer is safe and reported approximately 80% of men require no further prostate-cancer-directed treatment.2 This study investigated whether targeted focal therapy using ExAblate MRI-guided focused ultrasound can safely treat Gleason Grade Group 2/3 prostate cancer patients in a single-arm, multicenter phase IIb clinical trial.

 

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Men with MRI-visible intermediate-risk prostate cancer (PSA <= 20ng/mL, Grade Group 2 or 3, stage <= cT2b) and no prior cancer-directed treatment were eligible for this multicenter Phase IIb study (NCT01657942). Exclusion criteria included contraindications to MRI, calcification >2 mm from the targeted treatment area, and rectal pathology (fibrosis, stenosis) preventing safe probe insertion. Enrolling sites included seven academic centers and one private practice setting. Focal MRI-guided focused ultrasound was delivered to the index lesion, with the targeted region contoured to include the MRI-visible lesion and up to 10mm margin of normal-appearing tissue. Concurrent Grade Group 1 prostate cancer foci were untreated. Safety (adverse events reported up to 24-months), oncologic outcomes (MRI-targeted systematic prostate biopsy at 6-and 24-months in all men), and genitourinary functional outcomes were assessed. The trial schema is as follows:

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There were 101 men treated from May 4, 2017, to December 21, 2018. The median age was 63 years and median PSA was 5.7ng/mL. The percentage of men treated with Grade Group 2 and 3 prostate cancer was 78% and 22%, respectively. No serious treatment-related adverse events were reported at 24-months. Ninety-six men (95%) had no evidence of Grade Group >= 2 prostate cancer in the treated area at 6 months, and 90 men (88%) had no evidence of Grade Group >= 2 prostate cancer in the treated area at 24 months. Additionally, 60% of men had no evidence of any Grade Group >= 2 prostate cancer anywhere in the prostate gland at 24 months, including prostate cancer detected outside of the treatment area. Serum PSA measurements decreased after treatment and stabilized after six months:

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International Index of Erectile Function-15 (IIEF-15) erectile function scores were slightly worse at 24 months than at baseline (mean score difference of -3.5, 95% CI -5.4 to -1.6). At 24 months, 13% of patients reported no sexual activity and 81% achieved erections adequate for intercourse (IIEF q2 score >= 2):

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Lower urinary tract symptoms, assessed by IPSS, were similar at baseline and at 24 months (mean score difference 1.1, 95% CI 0.33-1.80):

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Finally, the estimated probability of urinary continence and 95% intervals over time are displayed in the following figure (urinary continence is defined as ICIQ <10):

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 Dr. Ehdaie concluded his presentation with the following take-home messages:

  • ExAblate MRI-guided focused ultrasound focal therapy using real-time MR thermometry is safe, has favorable quality of life outcomes compared to radical prostatectomy, and demonstrates durable oncologic outcomes for men with Grade Group 2 and Grade Group 3 prostate cancer based on 6- and 24-month biopsy
  • Patient-reported sexual function and urinary continence after MRI-guided focused ultrasound focal therapy is superior to studies evaluating radical prostatectomy and external beam radiotherapy
  • These data support a randomized controlled trial in men with intermediate-risk prostate cancer seeking to avoid radical whole-gland treatment

Presented by: Behfar Ehdaie, MD, MPH, Memorial Sloan Kettering Cancer Center, New York, NY

Co-Authors: Clare Tempany, Ford Holland, Adam Kibel, Quoc-Dien Trinh, Jeremy Durack, Oguz Akin, Andrew Vickers, Dan Sperling, Jeffrey Wong, Bertram Yuh, David Woodrum, Lance Mynderse, Steven Raman, Allan Pantuck, Marc Schiffman, Timothy McClure, Pejman Ghanouni, Geoffrey Sonn

Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Assistant Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2021 American Urological Association, (AUA) Annual Meeting, Fri, Sep 10, 2021 – Mon, Sep 13, 2021.

References:

  1. Hamdy FC, Donovan JL, Lane JA, et al. 10-Year Outcomes after Monitoring, Surgery, or Radiotherapy for Localized Prostate Cancer. N Engl J Med 2016;375(15):1415-1424.
  2. Guillaumier S, Peters M, Arya M, et al. A multicentre study of 5-year outcomes following focal therapy in treating clinically significant nonmetastatic prostate cancer. Eur Urol. 2018 Oct;74(4):422-429.
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