Presented by: Omer Sadeh MD
Department of Urology, Rambam Health Care Campus, Haifa, Israel

Introduction

High-intensity focused ultrasound (HIFU) is gaining increased popularity as a minimally invasive therapy for low to intermediate risk prostate cancer (PCa). Optimal recommendations for follow-up after treatment have yet to be defined.  Currently, prostate-specific antigen (PSA), multiparametric magnetic resonance imaging (mpMRI) and biopsies are used.  However, mpMRI after intervention is often inaccurate.

We aimed to investigate whether prostate-specific membrane antigen (PSMA-11) positron emission tomography (PET)/CT could be used to detect and localize recurrent disease.   

Materials

HIFU for PCa is performed in our institution under an ongoing investigational trial. Hemi-gland ablation is applied to the entire prostate lobe diagnosed with PCa on pre-treatment biopsy. Per protocol, patients complete an mpMRI and PSMA PET/CT 1 year after treatment. Repeat biopsy is left at physician discretion. Interim analysis was performed for the findings from the first 4 years of the trial. PSMA PET/CT scans were read by a masked nuclear radiologist. A 5-point Likert scale was defined to rate the suspicion for recurrence from very low risk (1) to very high risk (5) in each prostate lobe, with 4 used as a cutoff for suspected disease. Results were compared with template biopsy findings.

Results

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35 patients underwent HIFU in our institution from 04/2018 to 01/2022. Of them 15 patients completed both PSMA PET/CT and biopsy at 1 year. The hemi-gland based sensitivity, specificity, positive and negative predictive values for PSMA PET/CT were 50%, 44%, 37 and 57%  for in-field recurrence, and 66%, 91%, 66%, and 91% respectively for out-field recurrence. PSMA PET/CT was negative in one case with grade group (GG) 3 disease, and in 3 cases with GG 2 disease.

Conclusion

Our preliminary results indicate that PSMA PET/CT as a single modality is not sensitive enough for detection of in-field PCa recurrence after HIFU. Combination with mpMRI results may improve detection rates.

Funding

None

Co-Authors

Hanan Harbosh, MD
Nuclear Medicine, Rambam Health Care Campus, Haifa, Israel

Zohar Keidar, MD
Nuclear Medicine, Rambam Health Care Campus, Haifa, Israel

Gilad Amiel, MD
Department of Urology, Rambam Health Care Campus, Haifa, Israel