What are the considerations for using High-Intensity Focused Ultrasound (Hifu) for medical treatment?

High-Intensity Focused Ultrasound (HIFU) for Medical Treatment

HIFU should not be recommended as a standard treatment option for prostate cancer and should only be offered within the context of a clinical trial due to limited comparative outcome evidence and variable long-term oncological results. 1

Current Status of HIFU in Prostate Cancer Treatment

Evidence-Based Recommendations

• HIFU is not considered a standard care option for prostate cancer treatment according to multiple guidelines 1
• The American Urological Association (AUA), American Society for Radiation Oncology (ASTRO), and Society of Urologic Oncology (SUO) explicitly state that HIFU should be offered only within clinical trials 1
• European Association of Urology (EAU) guidelines similarly recommend HIFU only within clinical trials or well-designed prospective registries 1

Risk Stratification and HIFU Considerations

For different risk categories of prostate cancer:

1. Low-risk localized prostate cancer:

   • HIFU is not a standard treatment option 1
   • Should only be considered within clinical trials 1

2. Intermediate-risk localized prostate cancer:

   • Clinicians should inform patients that HIFU is not a standard care option 1
   • Comparative outcome evidence is lacking 1

3. High-risk localized prostate cancer:

   • HIFU is explicitly not recommended outside of clinical trials 1
   • Poor long-term oncological outcomes have been demonstrated 1

Efficacy and Outcomes

Oncological Outcomes

• Failure-free survival rates for focal HIFU vary significantly:
  • 44-65% at 3 years depending on definition of clinically significant prostate cancer 2
  • 88% failure-free survival at 5 years in some case series 1
• In-field recurrence rates up to 22% and out-of-field progression up to 29% have been reported 3
• Risk factors for recurrence include higher ISUP grade group, more positive cores at biopsy, and bilateral disease 3

Functional Outcomes

• Expected improvements in functional outcomes have not consistently materialized 1
• Whole-gland HIFU treatment has shown:
  • 12% incontinence rates 1
  • 61% erectile dysfunction rates 1
• Focal HIFU shows better functional preservation:
  • 98% continence rates at 6 months 3
  • 80% preservation of sufficient erections for sexual intercourse 3
  • 21% meaningful worsening in erectile function in recent studies 2

Technical Considerations and Patient Selection

Ideal Candidates for HIFU (if used within clinical trials)

• Prostate size less than 40cc 4
• Anterior-posterior dimension up to 35mm 4
• Localized disease (stage T1-T2) 5
• No prior transurethral resection of the prostate defects (relative contraindication) 1

Technical Limitations

• HIFU faces challenges delivering energy to the anterior part of large prostates 1
• Tumor location may influence oncological outcome 1
• The procedure involves 2-3 second bursts of ultrasound energy followed by cooling cycles 4

Monitoring and Follow-up

Post-HIFU Surveillance

• Regular follow-up biopsies are crucial for detecting recurrence 2
• MRI has shown poor performance in detecting residual disease (negative predictive value up to 89%) 2
• PSA monitoring alone is unreliable for detecting recurrence 2

Complications and Side Effects

Common Complications

• Urinary retention: <1-20% 5
• Urinary tract infections: 1.8-47.9% 5
• Stress or urinary incontinence: <1-34.3% 5
• Erectile dysfunction: 20-81.6% 5
• Recto-urethral fistula: <2% 5

Future Directions

The future of HIFU may lie in:

1. Focal therapy for small, low or intermediate-risk unifocal tumors 1
2. Salvage therapy for patients who have failed radiation therapy 1
3. Treatment for patients contraindicated for radical treatments due to comorbidities 1

Important Caveats

1. Limited long-term data: Most studies have short to medium-term follow-up
2. Lack of standardization: No consensus on patient selection criteria or treatment protocols
3. Monitoring challenges: Difficulty in reliably detecting recurrence with conventional methods
4. Variable outcomes: Significant heterogeneity in reported oncological and functional outcomes

HIFU remains an evolving technology that shows promise but requires further evaluation through well-designed clinical trials before it can be recommended as a standard treatment option for prostate cancer.