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MRI-guided high-intensity focused ultrasound (HIFU) is effective in patients with intermediate-risk prostate cancer, researchers reported.

According to the team's multicenter, single-arm, phase IIb study of 101 patients who received the treatment, 96% had no evidence of grade group 2 or higher prostate cancer on 6-month MRI-targeted and systematic biopsy in the treated area of the prostate gland, said Behfar Ehdaie, MD, of Memorial Sloan Kettering Cancer Center in New York City, and colleagues.

Similarly, 24-month results showed no evidence of grade group 2 or higher disease in 88% of 89 patients, the investigators reported in .

They also found there were few side effects with HIFU focal therapy, and that quality-of-life outcomes "compared very favorably" with those from studies of whole-gland treatments, such as radical prostatectomy or radiotherapy.

"These results support focal therapy for select patients and its use in comparative trials to determine if a tissue-preserving approach is effective in delaying or eliminating the need for radical whole-gland treatment in the long term," the team wrote.

The study was conducted at eight healthcare centers in the U.S. and included men age 50 or older with unilateral, MRI-visible, primary, intermediate-risk, previously untreated prostate adenocarcinoma (prostate-specific antigen [PSA] ≤20 ng/mL, grade group 2 or 3; tumor classification ≤T2) confirmed with combined MRI-targeted and systematic biopsies.

All patients underwent biopsies 6 and 24 months after the procedure, with oncologic efficacy defined as the absence of cancer grade 2 or higher at those time points.

Other results of the study included:

• No evidence of grade group 2 or higher cancer anywhere in the prostate gland in 76% of men at 6 months and in 60% at 24 months

• At the 6-month biopsy, 19 of the 101 men had newly detected grade group 2 or higher cancer outside of the treatment area only

• PSA declined after treatment at 6 months (mean decrease of -3.0 ng/mL, 95% CI -3.6 to -2.4) before rising slightly at 24 months (-2.6 ng/mL, 95% CI -3.3 to -2.0)

Quality of Life/Adverse Events

Erectile function scores as measured by the international index of erectile function were slightly worse at 24 months than at baseline (-3.5, 95% CI -5.4 to -1.6). Mean intercourse satisfaction (-1.8, 95% CI -2.9 to -0.8), and overall satisfaction scores (-0.8, 95% CI -1.3 to -0.3) were also slightly worse at 24 months.

"Although the difference in mean erectile function scores was significant, the small difference should be interpreted across the range of the overall score and considered across the time range of 2 years, in which small decreases in erectile function score are expected without treatment, making this change statistically but not clinically significant," the authors noted.

"These functional outcomes compare very favorably to patient-reported outcomes after whole-gland treatments, such as radical prostatectomy and radiotherapy, which, although effective, are associated with substantial and persistent side-effects that impact quality of life," the researchers added.

Regarding lower urinary tract symptoms, "most patients reported moderate or mild lower urinary tract symptoms at baseline and throughout the study period," with none of the patients reporting urinary incontinence requiring pad use at 24 months, the investigators said.

There were no serious treatment-related adverse events (AEs) observed during the study period. A single grade 3 urinary tract infection related to the device or procedure was reported, which resolved within 3 days.

Common grade 2 or lower AEs included hematuria in 24% of patients and urinary retention in 15%.

Study limitations, Ehdaie and colleagues said, included that 24-month biopsy is not a sufficient surrogate endpoint for metastases or cancer-specific death. "However, the aim of the study was to evaluate whether using MRI-guided focused ultrasound focal therapy can avoid whole-gland treatment based on biopsy outcomes after treatment; the detection of metastases is unlikely in an intermediate-risk prostate cancer cohort during the 2-year study period," the researchers pointed out.

They also noted that with the absence of a comparator arm of men randomized to active surveillance (AS), it was not possible to estimate the long-term clinical benefit of treating men with intermediate-risk prostate cancer rather than following them on AS.

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