Abstract
Focal therapy is a minimally invasive alternative treatment for localized prostate cancer (PC) aiming to achieve oncological control while preserving urinary and sexual functions. High-intensity focused ultrasound (HIFU) and high-intensity directional ultrasound (HIDU) enable precise prostate ablation guided by real-time transrectal ultrasound or magnetic resonance imaging (MRI) fusion imaging. This review evaluates the current status and prospects of ultrasound technology in the treatment of PC. HIFU provides precise tumor ablation with minimal damage to the surrounding tissues, whereas HIDU allows MRI-guided transurethral treatment with real-time thermometry. Clinical studies have reported favorable biochemical recurrence-free survival and functional outcomes. In Japan, a multi-institutional prospective study on focal therapy using HIFU has been approved as an advanced medical technology by the Minister of Health, Labor, and Welfare. This study compared the oncological and functional outcomes of HIFU-based focal therapy and radical prostatectomy in pair-matched patients to evaluate the effectiveness of HIFU in treating localized PC. HIFU induces immunogenic cell death, releases tumor-associated antigens, and reduces immunosuppressive cells. Low-intensity focused ultrasound enhances tumor immunogenicity by promoting heat shock protein expression and CD8(+) T cell activation. In conclusion, HIFU and HIDU offer effective focal therapy options for localized PC, and the immunomodulatory properties of HIFU and low-intensity focused ultrasound may benefit advanced PC treatment. Future studies should optimize patient selection by developing advanced imaging technologies and predictive models capable of visualizing MRI-invisible lesions and accurately detecting micro-metastatic disease. Moreover, evaluating long-term outcomes and exploring their combination with immunotherapy to enhance oncological efficacy will be essential.