High Intensity Focused Ultrasound for the Treatment of Prostate Cancer: Assessing Location of Failure after Focal Therapy in Prostate Cancer and Review of Histological Characteristics and Clinicopathologic Correlates after Treatment: A 5-Year Experience.

Abstract Background High-intensity focused ultrasound (HIFU) is a noninvasive treatment option used for localized prostate cancer or salvage surgery after failed radiation therapy. Histological changes in post-treatment biopsies are reviewed to better understand HIFU failures. Design Between 2016 and 2021, 50 patients with localized prostate cancer were enrolled and treated in this study. Of these, 10 patients underwent salvage therapy following radiation failure and 7 did not have post-treatment biopsies available for review and were excluded. Inclusion criteria included pathologically confirmed prostate cancer and clinical stage T1/T2 disease. We describe the histological changes in post-treatment biopsies as part of routine follow-up. Biopsies were examined for presence, distribution and extent of residual adenocarcinoma, Gleason score, and ablative tissue changes. Results A total of 33 patients underwent HIFU hemi-ablation treatment of localized prostate cancer as primary treatment with post-treatment biopsies available for review. The average mean age of the patients was 64 years (range 52-81 years). The average PSA level of the patients was 6.3 ng/mL (range 2.4-14.7 ng/mL). The Gleason score in pre-treatment prostate needle biopsies are as follows: 3+3: 1 (3%), 3+4: 21 (64%), 4+3: 9 (27%), 4+4: 1 (3%). In post-treatment prostate needle biopsies, 33 cases (100%) showed variable degree of fibrosis ranging from mild to moderate. 24/33 cases (73%) showed necrosis usually associated with acute and/or chronic inflammation. Histological examination of benign glands revealed glandular heterogeneity including atrophy and basal cell hyperplasia. 8 cases (24%) had residual prostatic adenocarcinoma after treatment, of which 4 cases were Gleason score: ≥3+4. In cases with residual adenocarcinoma, 8 cases (100%) showed nuclear enlargement, 5 cases (63%), cytoplasmic vacuolization and 1 case (13%) showed nuclear pyknosis, otherwise no discernable effects of treatment were seen. Conclusions Morphological alterations included a spectrum of changes ranging from extensive coagulative stromal necrosis secondary to thermal injury to atrophic changes in benign prostatic tissue after HIFU treatment. Our findings also support the hypothesis that HIFU failure results from inadequate targeting rather than failure within a treated zone.