Determining optimal patient selection for high-intensity focused ultrasound (HIFU) for prostate cancer: Results from a single-institution cohort.

362 Background: High-intensity focused ultrasound (HIFU) uses magnetic resonance imaging (MRI) and transrectal ultrasound to target areas affected by prostate cancer (PCa). HIFU has moderate PCa control outcomes with little impact on sexual or urinary side effects, but there is concern for disease recurrence and need for salvage treatment. Here we share institutional biopsy-proven recurrence and treatment failure outcomes following HIFU and identify clinicodemographic factors associated with adverse outcomes. Methods: All men who underwent robotic HIFU (Focal One) in 2021-2023 at the University of California, San Francisco and underwent 1-year post-procedure MRI-fusion biopsy were included. The primary outcome was treatment failure, defined as salvage treatment or metastases. Secondary outcomes were in-field recurrence, defined as Gleason Grade 2 (≥GG2) in the same region of HIFU treatment, overall recurrence, defined as ≥GG2 diagnosed anywhere in the prostate, and change in urinary and sexual function by International Prostate Symptom Score (IPSS) and Sexual Health Inventory for Men (SHIM) scores, respectively. Cox Proportional Hazards regression models and multivariable logistic regression and were used to estimate associations between clinical characteristics and outcome events. Results: Of 133 men who underwent HIFU, 110 had post-HIFU biopsy follow-up at median (IQR) of 12.5 (12-14) months. 18 (16%) had treatment failure, and median (IQR) time from recurrence to salvage treatment for 16 men was 3.5 (2-5) months. Cox proportional hazard regression showed pre-HIFU PSA to be associated with the risk of treatment failure (HR 1.14; 95% CI 1.05-1.24; p<0.01). Additional modeling comparing clinically relevant PSA groupings (<6, 6-10, and >10) revealed a significant association between treatment failure and PSA >10 (HR 5.35; 95% CI 1.54-18.57; p<0.01), but not PSA 6-10 (HR 1.94; 95% CI 0.53-7.06). In-field and overall recurrence on 1-year biopsy was 42% and 50%, respectively. On logistic regression analysis, pre-HIFU Gleason Grade of 3 or greater (≥GG3) was associated with a higher likelihood of in-field recurrence (OR, 3.11; 95% CI, 1.13-8.56), and both ≥GG3 (OR 3.07; 95% CI 1.04-9.10, p=0.04) and higher PSA (OR 1.20; 95% CI 1.05-1.37; p<0.01) were associated with a higher likelihood of overall recurrence. No significant differences were found for IPSS and SHIM scoring groups before and after HIFU. Conclusions: Treatment failure rate was 16%, and in-field and overall recurrence rates on biopsy one year after HIFU were 42% and 50%, respectively. Higher pre-HIFU PSA was associated with treatment failure and overall recurrence on biopsy, and ≥GG3 was associated with in-field and overall recurrence on biopsy. These findings emphasize the importance of careful patient selection for HIFU, which has potential for modest cancer control with minimal side effects in the appropriate PCa patient.