[Prostate cancer detection by assessing stiffness of different tissues using shear wave ultrasound elastog- raphy].

INTRODUCTION: Early detection of prostate cancer (PCa) remains a challenging issue. There are studies underway aimed to develop and implement new methods for prostate cancer screening by tumor imaging and obtaining tissue samples from suspicious areas for morphological examination. One of these new methods is shear wave ultrasound elastography (SWUE). The current literature is lacking sufficient coverage of informativeness and specificity of SWUE in the prostate cancer detection, there is no clear criteria for assessing tissue stiffness at different values of PSA and tumor grade, and in prostate hyperplasia and prostatitis.

AIM: To evaluate the informativeness and specificity of SWUE compared with other diagnostic methods.

MATERIALS AND METHODS: SWUE has been used in the Clinic of Urology of Sechenov First MSMU since October 2015. During this period, 302 patients were examined using SWUE. SWUE was performed with Aixplorer ultrasound system (Super Sonic Imagine), which provides a single-stage SWUE imaging with both B-mode and real-time mode. The first group (prospective study) included 134 men aged 47 to 81 years with suspected prostate cancer scheduled to either initial or repeat prostate biopsy. PSA levels ranged from 4 to 24 ng/ml. The second group (retrospective study) comprised 120 men with confirmed prostate cancer and PSA levels between 4 and 90 ng/ml. The third group (the control group), comprised 48 healthy men whose PSA level did not exceed 3 ng/ml. All patients of the groups 1 and 2 underwent a standard comprehensive examination. Patients in group 1 were subsequently subjected to transrectal prostate biopsy guided by localization of areas with abnormal tissue stiffness. PCa was detected in 100 of 134 patients. 217 patients of groups 1 and 2 underwent radical prostatectomy. In 28 of them, the match between the cancer location and differentiation in the removed prostate and SWUE findings before surgery was examined. Contrast-enhanced magnetic resonance imaging of pelvic organs was performed in 63 patients of groups 1 and 2.

RESULTS: Threshold values of stiffness (Emean) were determined, which normally range from 0 to 23 kPa, from 23.4 to 50 kPa in prostatic hyperplasia and 50.5 kPa and greater in prostate cancer. A total of 220 patients in groups 1 and 2 were found to have prostate cancer. The findings showed increased stiffness of prostate tissue depending on tumor differentiation, Gleason score, and hence, cancer risk. The sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV) were calculated for SWUE, biopsy based on 6 peripheral points used during SWUE, and for histologic findings from prostate cross sections. When compared to needle biopsy, Se, Sp, PPV, NPV for SWUE were 90.8, 94.6, 56.6 and 97.9%, respectively.

CONCLUSION: The study findings suggest a high diagnostic performance of SWUE in detecting prostate cancer.