MRI-guided Focal Treatment of Prostate Cancer

Take-Away Points

• ■ Major Focus: Phase II clinical trial of safety and oncologic outcome of focal treatment with high-intensity focused US (HIFU) under MRI guidance on intermediate-risk, clinically significant prostate cancer.

• ■ Key Results: Ninety-three percent of patients (44 total) remained disease free at biopsy performed 5 months after treatment. No significant change was found in median erectile function score, although larger ablation volumes were associated with decreased erectile function.

• ■ Impact: This study demonstrated the safety and favorable oncologic and functional outcomes of MRI-guided HIFU focal treatment for intermediate-risk prostate cancer. Future studies are needed with a larger cohort and better optimization of focal therapy treatment volumes.

Whole-gland prostatectomy or radiation remains the standard of care for localized clinically significant prostate cancer. However, whole-gland therapies commonly are associated with multiple adverse effects, such as erectile dysfunction. Focal therapies, including HIFU and cryotherapy, may produce good outcomes with fewer side effects.

This prospective phase II trial focused on men with unifocal, intermediate-risk, clinically significant prostate cancer visible at MRI. Forty-four patients underwent transrectal HIFU targeted at the tumor under MRI guidance to improve accuracy. MRI thermography was used to monitor the zone of treatment during the procedure.

Follow-up at 5 months showed only one patient with a grade 3 adverse event, with no major procedure-related adverse event. Ninety-three percent of patients were disease free at biopsy performed 5 months after treatment. While no statistically significant drop in overall score of erectile function or International Prostate Symptom Score occurred after treatment, targeted volume larger than or equal to 15 cm³ correlated with decreased erectile function at 6 weeks. These encouraging results represent a significant step toward wider acceptance of focal therapy in prostate cancer. Future prospective studies with larger cohorts of patients and follow-up time will need to focus on optimizing treatment volume and/or margin to minimize adverse effects and prevent residual or recurrent disease.

Highlighted Article

• Ghai S, Finelli A, Corr K, et al. MRI-guided focused ultrasound ablation for localized intermediate-risk prostate cancer: early results of a phase II trial. Radiology 2021;298(3):695–703. [Published correction appears in Radiology 2021;299(2):E258]. doi: https://doi.org/10.1148/radiol.2021202717