High-density focused ultrasound therapy for prostate cancer developed by Tokai University

On May 19th, at the Tokai University Shinagawa Campus (Takanawa, Minato-ku, Tokyo), Tokai University Hospital (Director Masahiko Watanabe) announced the commencement of clinical research involving "Targeted Localized Therapy for Prostate Cancer Using High Density Focused Ultrasound Therapy" under Advanced Medical Treatment B. This treatment method focuses on localized prostate cancer and utilizes precise diagnosis through magnetic resonance imaging (MRI) and ultrasonography. It involves using focused ultrasound for the thermal ablation of cancerous tissue while preserving the surrounding healthy tissue.

Currently, this procedure is exclusively available at Tokai University Hospital. However, there are plans for collaborations with other medical institutions to conduct this clinical research at multiple facilities. By mitigating the occurrence of posttreatment complications related to urinary and sexual functions, which are commonly observed with conventional treatments in these patients, this approach aims to enhance patients' quality of life (QOL).

In January of this year, the study, led by Associate Professor Sunao Shoji (Department of Surgical Science, School of Medicine) at the Tokai University Hospital, received approval as an "Advanced Medical Treatment B" from the Ministry of Health, Labour, and Welfare. This hospital has been conducting clinical research on this treatment since 2016, and over 300 cases have already been successfully treated using this therapy. With the approval of Advanced Medical Treatment B, this team will now begin new clinical research. Researchers from other research institutions in other fields, such as statistics, and relevant companies are expected to participate in this research.

This new clinical study aims to verify the effectiveness and minimally invasive nature of a particular treatment by comparing it with robot-assisted radical prostatectomy in a sample of 310 cases. Furthermore, this research will evaluate the recurrence-free survival rate and the occurrence of urinary incontinence through a follow-up observation period of 5 years. It is anticipated that it will take approximately 8 years to acquire this data.

Shoji commented, "Our current work on cancer-targeted local therapy has already shown promising results in terms of efficacy and minimal invasiveness in selected patient cases. We aim to demonstrate these findings through clinical research under Advanced Medical Treatment B. Once the data have been acquired, we believe that this treatment method will establish itself as one of the standard therapies for prostate treatment in Japan, providing renewed hope for many patients."

Prostate cancer is the most common cancer among men, and the number of patients and related deaths has been increasing annually due to factors such as aging and lifestyle changes. With advances in diagnostic accuracy and the implementation of screening in health checkups, approximately 95,000 people in Japan were diagnosed with prostate cancer in 2019. Although about 80% of these cases were classified as early-stage (nonmetastatic) cancer, approximately 13,000 people died from this cancer in 2020.

If the value of the blood test for the prostate-specific antigen (PSA) exceeds the age-specific reference range, a prostate biopsy is conducted to obtain tissue for a pathological diagnosis. In this procedure, a biopsy needle is randomly inserted into the prostate to collect tissue. Therefore, the cancer may be missed if it is located in an area that the biopsy needle cannot reach. PSA levels increase not only with prostate cancer but also with age, and elevated levels can occur even when prostate enlargement or other noncancerous conditions are absent. For this reason, it is recommended that men undergo a follow-up examination after a few years.

In contrast, Shoji's research group has been conducting "MRI-TRUS Fusion Image-Guided Transrectal Prostate Biopsy" since 2013, which combines MRI and ultrasound diagnostics to accurately locate the cancer within the prostate. This diagnostic method was certified under "Advanced Medical Treatment A" in 2016 and has been covered by insurance in Japan since April 2022. Currently, this examination has been implemented in approximately 40 facilities nationwide.

This examination enables the visualization of suspicious areas in a three-dimensional image by depicting the trajectory of the biopsy needle. By developing a system that guides the needle using computer-processed image data, a more precise diagnosis and depiction of prostate cancer can be achieved. There are various types of prostate cancer, including multiple, localized, and low-grade types, which have traditionally been difficult to distinguish clearly. However, the examination procedure facilitates the identification of these different types.

In this treatment, specific areas to be exposed to focused ultrasound are determined based on the data obtained from the above examination. The treatment involves using focused ultrasound beams emitted from a probe inserted through the rectum to destroy prostate tissue, while using ultrasound imaging as confirmation. By utilizing the characteristic of focused ultrasound to generate high temperatures only within the focal region, cancer cells are thermally coagulated and necrotized. This targets localized prostate cancer, which is estimated to account for approximately 20−30% of all prostate cancer cases without metastasis.

In advanced medical treatment for prostate cancer, the examination is used to diagnose localized prostate cancer. The goal is to treat the cancer while preserving normal tissue as much as possible.

Since 2016, the hospital has conducted this treatment in over 300 cases, and the clinical research results of the initial 90 cases were published in an international academic journal in 2020. The following results were reported: the median treatment time for this therapy was 39.5 minutes (as compared to approximately 3 hours for robotic surgery), patients were discharged within 24 hours after treatment, the remission rate of cancer was 92.2% (over a period of 12−42 months), urinary incontinence occurred in no patients, and the erectile preservation rate was 70%.

The medical expenses for this treatment are approximately 1 million yen when fully self-funded. However, in cases where mixed treatment involving advanced medical treatment is administered, hospitalization and outpatient costs are covered by insurance. If a patient is enrolled for advanced medical insurance and eligible for a 30% copayment, the medical expenses can be approximately 100,000 yen. The ongoing costs of this surgery are lower compared to those of robotic surgery.

The standard treatments for prostate cancer are surgical removal or radiation therapy, but both treatment options have their challenges. For example, in robot-assisted surgery, approximately 20% of patients experience urinary incontinence within 12 months after the procedure, while radiation therapy can lead to bleeding in the bladder and rectum. It has also been reported that both these treatments result in erectile dysfunction, with rates approximately 7−55%.