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Emerging therapies

Emerging therapies

Focused ultrasound controls prostate cancer with fewer side effects

02 Aug 2022
Behfar Ehdaie
Behfar Ehdaie: “To draw a parallel with how breast cancer treatment changed 30 years ago, you could think of focal therapy as a ‘male lumpectomy’. Instead of removing all the tissue in a breast or prostate, we have learned that it is safe and effective to treat specific areas and greatly reduce the burden on patients.” (Courtesy: Memorial Sloan Kettering Cancer Center)

Focal therapy using MRI-guided focused ultrasound is safe and effective for men with intermediate-risk prostate cancer who seek to avoid more invasive treatments, according to the results of a new clinical study. The first-of-its-kind phase 2 trial, described in Lancet Oncology, found that two years after treatment, 88% of participants had no evidence of intermediate- or higher-risk prostate cancer in the treated area.

Treatments for intermediate-risk prostate cancer include radical prostatectomy and radiotherapy and are traditionally directed at the whole prostate gland. But men who undergo such treatments often have persistent side effects, such as urinary and sexual problems, that could reduce their quality-of-life. In contrast, focal therapy only treats areas of malignancy within the prostate, preserving normal prostate tissues outside of the treatment margins.

Led by principal investigator Behfar Ehdaie of the Memorial Sloan Kettering Cancer Center, the study took place at eight healthcare centres in the USA (seven academic and one private). The teams treated 101 newly diagnosed patients with grade group 2 (78%) or 3 (12%) prostate cancer visible on MRI and confirmed on combined (MRI-targeted and systematic) biopsy.

Treatments were performed using a closed-loop MRI-guided focused ultrasound system that combines a transrectal ultrasound transducer with MRI of the pelvis. The MR imaging visualizes the target tumour, monitors the therapy with MR thermometry, and evaluates the ablated tissue immediately after treatment.

Ehdaie and colleagues explain that the ExAblate phased-array transducer directs acoustic energy to the targeted location, heating the tissue to ablative temperatures of 60-70 °C, guided by real-time MRI-based temperature feedback. The target was the MRI-visible lesion plus a margin of 5–10 mm of surrounding healthy-looking tissue.

Sonications were swept across the target slice-by-slice through the prostate gland and repeated until the target was covered by the required thermal dose. After each sonication, the researchers acquired anatomical MRI to enable modification of the treatment plan to account for treatment-induced changes in the gland volume. The median duration for the entire procedure was 110 min.

The researchers assessed the safety of the therapy every 90 days in the first year after treatment, and at 18 and 24 months. All patients also underwent combined prostate biopsy six and 24 months after the procedure. No serious treatment-related adverse effects occurred during the 24-month observation period, with only one grade 3 adverse event (urinary tract infection that resolved within three days) reported. Self-reported erectile and urinary function scores were slightly lower than at baseline, but compared very favourably to patient-reported outcomes after whole-gland treatments.

At six months, 96 of the 101 patients had no evidence of grade group 2 or higher prostate cancer in the treated area of the prostate gland. The six-month biopsy identified that 19 of the men had newly detected grade group 2 or higher prostate cancer outside of the treatment area. The researchers suspect that rather than being new sites of cancer, these were likely tumours that were undetected before treatment.

At 24 months, 11 of the 89 patients evaluated did have cancer detected in the treatment area, three of whom had grade group 4 or higher cancer. These patients were referred for conventional whole-gland treatment.

The authors cite three key strengths of their study: the patient cohort was geographically diverse; none of the enrolled patients had low-grade prostate cancer; and, in spite of this, findings were comparable with other prospective focal therapy clinical trials with lower-risk patients.

In the future, the research team will focus on delivering a randomized controlled trial to determine the effectiveness of focal therapy compared with managing prostate cancer with active surveillance. “Overall, avoiding whole-gland treatments will reduce the side-effects associated with surgery and radiation, including sexual, urinary and bowel dysfunction,” comments Ehdaie.

“Further, future studies will also report the impact of salvage treatment in patients with disease progression after focal therapy,” says Ehdaie. “The goal is to provide a treatment option for men diagnosed with prostate cancer along the spectrum of successful options spanning from active surveillance to whole-gland treatment and prolong life and preserve quality-of-life.”

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