MR-guided focal therapy emerges as alternative to radical therapy for intermediate-risk prostate cancer

In some men with intermediate-risk prostate cancer, magnetic resonance (MR)–guided focused ultrasound (MRgFUS) focal therapy may be an effective alternative to radical therapy that improves quality-of-life measures such as sexual function and urinary incontinence, according to findings shared during the 2021 AUA Annual Meeting.¹

Behfar Ehdaie, MD

“ExAblate MR-guided focal therapy using real-time MR thermometry preserves urinary incontinence and sexual function and it’s effective for grade group 2 and 3 prostate cancer cancers based on 2-year biopsy outcomes,” said lead author Behfar Ehdaie, MD, MS, a urologic surgeon at Memorial Sloan Kettering Cancer Center. “ExAblate MR-guided focused ultrasound may enable men to consider a tissue preserving approach and defer or avoid radical therapy.”

Final results from a phase 2b study (NCT01657942) of MRgFUS showed that at 24 months, 88% of men had no evidence of grade group 2 or 3 prostate cancer in the treatment area according to targeted prostate biopsy. Additionally, 60% of men had no evidence of grade group 2 or 3 disease anywhere in the prostate gland, including outside of the treatment area. Serum PSA levels decreased by almost 50% after treatment and stabilized after 6 months.

Ehdaie said that men who undergo prostatectomy or radiation therapy often experience significant declines in erectile function and urinary incontinence. Data from a study of 3262 men published in 2020 showed that, at 12 months, about 60% experienced erectile dysfunction following nerve-sparing radical prostatectomy and approximately 50% experienced the same following external beam radiation therapy.² Men who have intermediate-risk prostate cancer, grade group 2 or 3, are often ineligible for active surveillance or experience early disease progression, up to 40% in findings from the ProtecT trial (NCT02044172), leading to surgery or radiation therapy.³

Ehdaie and colleagues explored MRgFUS as an alternative therapy that reduces side effects while maintaining cancer control by targeting areas of no cancer within the prostate gland. He said the ExAblate MR-guided focus ultrasound device delivers targeted high intensity focused ultrasound therapy through the rectum. Ehdaie added that multicenter retrospective studies have shown focal therapy for prostate cancer is safe, and approximately 80% of men require no further prostate cancer-directed treatment.⁴

Investigators evaluated MRgFUS in a single arm, multicenter trial. Men (N = 101) were treated at 7 academic centers and 1 private practice. MRgFUS was delivered focally to the lesion with a margin of normal tissue of greater than or equal to 5 mm based on planning. Treatment was monitored with real-time MR thermometry. Concurrent grade group 1 prostate cancer foci were not treated.

Men with untreated unilateral and more visible, grade group 2 or 3 prostate cancer were eligible. Patients were excluded if they were unable to undergo MRI or had large calcification between the rectum and the planned targeted treatment zone that could interfere with treatment.

Patients underwent targeted and systematic biopsies at 6 and 24 months after treatment, and examinations with quality of life measurements every 3 months.

The primary end points were efficacy and safety. Secondary end points included change in baseline patient-reported quality of life at 24 months.

The average patient age was 63 years and 86% of the cohort was White. The median PSA was 5.7 ng/mL. Eighty-four patients had at least clinical stage T1c disease. Seventy-eight percent of patients were in grade group 2 and 22% were in grade group 3.

Ehdaie said investigators recorded no serious adverse events (AEs). Most minor or moderate AEs self-resolved by 90 days. Two patients had ejaculation disorder and 1 had hematospermia beyond 90 days.

Erectile function scores were slightly worse at 24 months compared with baseline (HR, -3.5; 95% CI, -5.4 to -1.6). Ten (13%) reported no sexual activity and 81% of patients achieved erections adequate for intercourse.

Lower urinary tract symptoms were similar at baseline and 24 months (mean score difference, 1.1; 95% CI, 0.33-1.8).

“Overall, approximately 75% of men were able to achieve functional reactions after treatment at 24 months without starting a new erectile function medication,” Ehadie said. “No patients reported urinary incontinence and the estimated probability of urinary continence over time was excellent.”

References

1. Ehadie B, Tempany C, Holland F, et al. MRI-guided focused ultrasound (MRgFUS) focal therapy for intermediate-risk prostate cancer: final results of a phase IIb multicenter study. Presented at: 2021 American Urological Association Annual Meeting; September 10-13, 2021; virtual. Abstract LBA02-12.

2. Hoffman KE, Penson DF, Zhao Z, et al. Patient-reported outcomes through 5 years for active surveillance, surgery, brachytherapy, or external beam radiation with or without androgen deprivation therapy for localized prostate cancer. JAMA. 2020;323(2):149-163. doi:10.1001/jama.2019.20675

3. 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. doi: 10.1056/NEJMoa1606220

4. 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;74(4):422-429. doi:10.1016/j.eururo.2018.06.006