A novel magnetic resonance imaging (MRI)-guided procedure that uses therapeutic ultrasound may effectively treat prostate cancer with minimal side effects, according to a new study presented at the 2019 annual meeting of the Radiological Society of North America (RSNA) (Abstract SSC07-07). Researchers added that the incision-free technique could also be used to treat benign enlargement of the prostate gland.
How TULSA Works
In recent years, a minimally invasive method called MRI-guided transurethral ultrasound ablation (TULSA) has emerged as a promising treatment option for prostate cancer. TULSA works by delivering precise doses of sound waves to diseased prostate tissue, while sparing the healthy nerve tissue surrounding the prostate. TULSA relies on a rod-shaped device that is inserted into the urethra. The novel device has 10 ultrasound-generating elements that can cover the entire prostate gland. One or more of the elements are used to send out soundwaves that heat and destroy the target prostate tissue. The elements are controlled automatically by a software algorithm that can adjust the shape, direction, and strength of the therapeutic ultrasound beam. The entire procedure takes place in an MRI scanner so that doctors can closely monitor treatment and assess the degree and location of heating.
“There are two very unique things about this system...First, you can control with much more finesse where you're going to treat, preserving continence and sexual function. Second, you can do this for both diffuse and localized prostate cancer and benign diseases, including benign hyperplasia.”— Steven S. Raman, MD
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“Unlike with other ultrasound systems on the market, you can monitor the ultrasound ablation process in real time and get immediate MRI feedback of the thermal dose and efficacy,” said study co-author Steven S. Raman, MD, Professor of Radiology and Urology and Director of Prostate MR Imaging and Interventions and Prostate MR Imaging Research at the University of California, Los Angeles. “It's an outpatient procedure with minimal recovery time.”
Researchers reported on the 12-month outcomes from the TULSA-PRO ablation clinical trial (TACT). The multicenter study enrolled 115 men (median age = 65) with localized low- or intermediate-risk, gland-confined prostate cancer. Clinicians delivered TULSA treatment to the entire gland. Treatment time averaged 51 minutes.
Prostate volume in the study group decreased on average from 39 cm3 pretreatment to 3.8 cm3 1 year after treatment. Overall, clinically significant cancer was eliminated in 80% of the study participants. Seventy-two out of 111 men, or 65%, had no evidence of disease at biopsy after 1 year. Blood levels of prostate-specific antigen fell by a median of 95%. There were low rates of severe toxicity and no bowel complications.
“We saw very good results in the patients, with a dramatic reduction of over 90% in prostate volume and low rates of impotence with almost no incontinence,” said Dr. Raman.
Approved for clinical use in Europe, TULSA has just received 510(k) clearance from the U.S. Food and Drug Administration for prostate tissue ablation in the United States. Assuming follow-up studies support the preliminary results, the technique could develop into an important tool for treating both prostate cancer and benign prostatic hyperplasia.
“There are two very unique things about this system,” explained Dr. Raman. “First, you can control with much more finesse where you're going to treat, preserving continence and sexual function. Second, you can do this for both diffuse and localized prostate cancer and benign diseases, including benign hyperplasia.”
TULSA also has the benefit of allowing further treatment if needed, Dr. Raman said. If it fails, then the procedure can be repeated, and more aggressive invasive approaches like surgery and radiation therapy can still be used. Alternatively, TULSA may enable noninvasive treatment for localized radiation failure.
The study also supports the use of MRI for posttreatment monitoring of patients who undergo TULSA. MRI at 1 year after treatment had a negative predictive value of 93% to 96% for detecting residual cancer.
The authors concluded, “Whole-gland ablation using MRI-guided TULSA achieves predictable prostate-specific antigen and prostate volume reduction. Multiparametric MRI is promising for post-TULSA follow-up.”
Disclosure: For full disclosures of the study authors, visit meeting.rsna.org/program.