MP55-04: The Predictive Value of Tissue Change during Ultrasound Guided High Intensity Focused Ultrasound (USgHIFU) Focal Therapy on Treatment Success

Monday, May 16, 2022 8:45 AM to 10:00 AM · 1 hr. 15 min. (America/Chicago)
Room 225
Oncology: Prostate


Authors: Yash Khandwala*, Shravan Morisetty, Sulaiman Vesal, Richard E. Fan, Ahmed El Kaffas, Pejman Ghanouni, Mirabela Rusu, Geoffrey A. Sonn, Palo Alto, CA

Introduction: Focal therapy using USgHIFU to ablate localized prostate cancer is attractive to patients due to lower risk of erectile dysfunction and urinary incontinence compared to whole gland therapy. However, persistent cancer may occur in 30% of cases due to failure to reach target temperature in certain regions of the planned ablation. During USgHIFU, monitoring of tissue change (TCM) through measuring backscattered echo signals is used as a surrogate for temperature change. We sought to validate the TCM score as a measure of tissue destruction and treatment success.

Methods: Clinical and TCM data were analyzed from 41 consecutive men who underwent focal USgHIFU at Stanford using the Sonablate device (Sonablate Corp, Charlotte, NC). TCM values (range .38 to 1.79) were extracted from every focal point across all patients. The patients were split into two groups based on overall median TCM score (0.64). Metrics for treatment success included loss of MR volume, post-treatment PSA nadir, and presence of cancer in the treated area on targeted biopsy at 1 year. We also assessed the association between median TCM values during the ablation and treatment success.

Results: Men with persistent cancer after USgHIFU treatment (n= 22) had lower median TCM scores compared to those with negative post-treatment biopsies (0.62 vs. 0.81, p = 0.022). Higher TCM scores were also associated with greater prostate destruction after accounting for index lesion volume. To assess tissue destruction after USgHIFU, a prostate extirpative ratio (PER) was defined to compare post-ablation volume with baseline volume (Figure 1). A lower PER indicates greater tissue destruction. The PER was 0.84 for patients with a median TCM score of > 0.64 vs. 0.94 for those with median TCM < 0.64 (p = 0.038). Men with a negative post-op MRI tended to have higher median TCM scores, 0.75 vs. 0.59, p= 0.020. After accounting for confounders, treatment with a median TCM score of > 0.64 had 79% lower odds of clinically significant disease on repeat biopsy.

Conclusions: A measure of intra-op tissue change during USgHIFU using backscattered echo signals is associated with prostate tissue destruction and improved oncologic outcomes. Urologists may use this metric during treatment to improve cancer destruction.

Source of Funding: None