Morphological analysis of the effects of intraoperative transrectal compression of the prostate during high‐intensity focused ultrasound for localized prostate cancer

Abstract

Abbreviations & Acronyms 3-D = three-dimensional BDFS = biochemical diseasefree survival rate DVC = dorsal vein complex HIFU = high-intensity focused ultrasound MRI = magnetic resonance imaging PSA = prostate-specific antigen PZ = peripheral zone TRUS = transrectal ultrasound TZ = transition zone Objectives: To evaluate the effects of transrectal compression of the prostate for intraoperative prostatic swelling and intraprostatic point shift during high-intensity focused ultrasound treatment of localized prostate cancer. Methods: Patients treated with whole-gland high-intensity focused ultrasound as primary monotherapy for localized prostate cancer were enrolled in the study. Using the standard and compression method, the volumes of degassed water in the balloon covering the high-intensity focused ultrasound probe were 50 mL and 80-160 mL, respectively. To identify prostatic swelling and shift during high-intensity focused ultrasound and the volume occupied by the non-enhanced area, three-dimensional prostate models were reconstructed using ultrasound and contrast-enhanced magnetic resonance imaging. Results: In comparison with the standard (n = 40) and compression (n = 48) methods, intraoperative increase in the prostate volume (21% vs 5.3%; P = 0.044), intraprostatic point shift (4 mm vs 2 mm, P = 0.040 in the transition zone; 3 mm vs 0 mm; P = 0.001 in the peripheral zone) and the volume occupied by the non-enhanced area (89% vs 96%; P = 0.001) were significantly suppressed. The biochemical disease-free survival rate in patients treated using the compression method was significantly improved relative to the standard method (92.6% vs 76.5%; P = 0.038). Regarding complications, there was no significant difference in the rate of urethral stricture (P = 0.9), urinary tract infection (P = 0.9), incontinence (P = 0.3), erectile dysfunction (P = 0.9) or recto-urethral fistula between the patients treated using the standard and compression methods. Conclusions: Intraoperative transrectal compression suppresses intraoperative increase in the prostate volume and intraprostatic point shift during high-intensity focused ultrasound, having the potential to achieve precise whole-gland and lesion-targeted focal therapy.

Analysis of oncological outcomes of whole-gland therapy with high-intensity focused ultrasound for localized prostate cancer in clinical and technical aspects: a retrospective consecutive case-series analysis with a median 5-year follow-up

“…In a previous report, intra-operative compression of the prostate suppressed prostate swelling during HIFU, which has the potential to contribute to the accurate treatment [10]. By means of prostate compression, prostatic pressure inside the fibrous prostatic capsule can be increased [13].…”

“…Because the major reason for prostatic swelling is rapidly induced diffuse stromal edema caused by HIFU in the pathological analysis [14], compression of the prostate would suppress the edema due to the highly increased intra-prostatic pressure. In previous reports, intraoperative increases in prostate volume (21 vs. 5.3%; p ¼ 0.044), intra-prostatic targeted point shift (4 mm vs. 2 mm, p ¼ 0.040 in the transition zone; 3 mm vs. 0 mm; p ¼ 0.001 in the peripheral zone), and the volume occupied by the non-enhanced area (89 vs. 96%; p ¼ 0.001) were significantly suppressed in the compression method compared with the conventional method, and the BDFS in patients treated with the compression method was significantly higher compared with those treated with the conventional method (92.6 vs. 76.5%; p ¼ 0.038) [10]. In the present study, the rates of blood flow disappearance in each patient were significantly higher in the patients who were diagnosed as having non-recurrence than those in the low-, intermediate-, and high-risk groups.…”

“…At 14 days to 28 days after the treatment, contrast-enhanced MRI was performed using a 1.5-Tesla magnet (Signa HD; GE Healthcare, Little Chalfont, UK) with an eight-channel cardiac coil for the evaluation of blood flow in the prostate. The details of postoperative contrast-enhanced magnetic resonance imaging (MRI) were detailed in previous literature [10]. The blood flow disappearance was evaluated on the final dynamic post-contrast image, and the volume of blood flow disappearance was measured using a three-dimensional (3 D) manually reconstructed, segmented MRI by two experienced radiologists using ZIO Station V R (AMIN, Tokyo, Japan).…”

“…A previous study reported that NHT with HIFU treatment exhibits significant clinical benefits to intermediate-and high-risk patients [9]. In terms of the technical aspects of HIFU, compared with conventional methods, intra-operative transrectal compression of the prostate inhibits prostatic swelling and intra-prostatic targeted point shift, and it leads to an increased volume of blood flow disappearance (89 vs. 96%; p ¼ 0.001) after HIFU and improved biochemical disease-free survival (BDFS) in the medium-term follow-up (92.6 vs. 76.5%; p ¼ 0.038) [10]. Because prostate swelling negatively correlates with preoperative prostate volume (r¼À0.484, p ¼ 0.001), suggesting that a smaller prostate likely has more swelling [11]; accordingly, the compression method may contribute to more efficacious treatment, especially in a smaller prostate.…”

Histotripsy: The Next Generation of High‐Intensity Focused Ultrasound for Focal Prostate Cancer Therapy

“…It has been noted that during treatment of prostate cancer with HIFU, the resulting edema causes the prostate to enlarge, which changes the targeting of the treatment zone. Endorectal compression of the prostate under US guidance appears to improve whole‐gland and lesion‐targeted therapy . Automated segmentation has been developed for US‐guided HIFU treatments …”