HIFU Treatment Failure Tied to Prostate Cancer Location – Renal and Urology News

The locations of prostate cancer lesions are the strongest predictors of treatment failure in men receiving high-intensity focused ultrasound (HIFU), investigators reported at the American Urological Association 2024 annual meeting (AUA 2024) in San Antonio, Texas. Another team at the meeting suggested that prostate-specific membrane antigen-positron-emission tomography/computed tomography (PSMA PET/CT) imaging can improve lesion detection and patient selection for focal therapies.

In a cohort of 77 patients who underwent HIFU, 18% experienced treatment failure, defined as the presence of grade group 2 or higher cancer at 12 months. Lesion location was the only factor associated with treatment failure among 16 variables in univariate logistic regression analysis, Simon John Christoph Soerensen, MD, PhD student, and senior researcher Geoffrey Sonn, MD, at Stanford University School of Medicine in California, reported on behalf of their team. Cancer involvement at the prostate base was significantly associated with a 3.6-fold increased risk of treatment failure with an area under the curve (AUC) of 0.63. Involvement of the mid-gland was protective, correlating with 78% decreased odds of failure and an AUC of 0.68. Peripheral zone lesions were less likely to result in failure compared with central gland lesions, with 78% decreased odds of failure and an AUC of 0.60.

“Cancers at the base of the prostate have a higher chance of recurring after HIFU than cancers in the middle of the prostate. This finding can help urologists better counsel patients interested in HIFU focal therapy about the chance of treatment failure,” the investigators said in an interview. “Technical modifications may be necessary to reduce focal therapy treatment failure for cancers in this location.”

In a separate study, Kylie Yen-Yi Lim, MBBS, of Monash University in Clayton, Victoria, Australia, and colleagues, evaluated whether adding PSMA PET/CT to the current diagnostic protocol would refine patient selection by improving detection of index prostate lesions and clinically significant out-of-field lesions.

In their retrospective review of data from 60 men who met MRI-based criteria for focal therapy but chose radical prostatectomy, pathology reports revealed that 40 men (66%) harbored disease characteristics that would have rendered them ineligible for focal therapy. Of the 40 men, 80% had bilateral grade group 2 or higher disease, 12.5% had large volume tumors, and 7.5% had extraprostatic extension.

Standard of care focal therapy criteria had a sensitivity, specificity, and positive predictive value of 71.4%, 80.3%, and 33.3%, respectively. The addition of PSMA PET/CT improved specificity to 89.7% and positive predictive value to 46.2%, while decreasing sensitivity to 64.3%, the investigators reported. The sensitivity and specificity of excluding out-of-field lesions using standard diagnostics were 55.8% and 91.2%, respectively. The addition of PSMA PET/CT enhanced detection of clinically significant out-of-field lesions by increasing sensitivity to 75.5%, the investigators reported.

Appropriate patient selection is critical for focal therapy success. Current criteria, defined by Delphi consensus, rely on MRI imaging results that indicate cancer foci less than 1.5 mL or if localized to one hemi-gland, less than 3 mL. Men also need to have a PSA less than 10 ng/mL and grade group or less.

“The current SOC diagnostics underestimate tumour volumes and bilateral disease,” Dr Lim’s team concluded in a study abstract. “The addition of PSMA PET/CT to the current SOC diagnostics improved characterisation of the index tumour and improved detection of out-of-field significant tumours.”

Dr Soerensen and Dr Sonn noted that they frequently obtain PSMA PET/CT prior to focal therapy with mixed results and look forward to additional research.

Prostate cancer ablation guidelines may emerge based on mostly expert opinion, they added, but data from comparative treatment trials are still needed.