Impact of a Novel Ultrasound Microvascular Imaging and Elastography on Prostate Cancer Classification

Ting-Ting Shen; Jun-Li Xue

Disclosures

Transl Androl Urol. 2019;8(6):696-702. 

In This Article

Abstract and Introduction

Abstract

Background: This study was aimed to compare the sensitivity of transrectal ultrasound (TRUS) guided systematic biopsy (TRUS-SB), superb microvascular imaging guided targeted biopsy (SMI-TB), and elastography ultrasound guided targeted biopsy (EU-TB) in detecting prostate cancer (PCa).

Methods: One hundred and eighty-four patients with suspicious PCa were randomly divided into two groups, SMI-TB group (n=92) and EU-TB group (n=92). All the patients received a 2-core SMI-TB or a 2-core EU-TB before receiving a 12-core TRU-SB depending on the group. The 2-core SMI-TB was conducted at the most increased vascularity areas rated by a radiologist on a semi-quantitative criterion. The 2-core EU-TB was performed at the dark blue areas that identified as suspicious areas. The PCa detection rate was compared among TRUS-SB, SMI-TB, and EU-TB in the total population and in two groups.

Results: PCa was detected in 65 out of 184 patients. The SMI-TB group patients received 1,272 cores in total with a positive rate of 23.81% (40/168) for SMI-TB cores and 4.17% (46/1,104) for TRUS-SB cores. The EU-TB group patients received a total of 1,262 cores with a positive rate of 31.01% (49/158) for EU-TB cores and 5.34% (59/1,104) for TRUS-SB cores. Targeted cores (27.30%, 89/326) achieved significantly higher sensitivity in PCa detection than systematic cores (4.76%, 105/2,208) (SMI-TB vs. TRUS-SB: OR 7.188, P<0.001; EU-TB vs. TRUS-SB: OR 7.962, P<0.001).

Conclusions: Superb microvascular imaging and elastography ultrasound guided targeted biopsy may result in higher prostate cancer detection rate as adjunct to gray-scale ultrasound guided systematic biopsy. However, targeted biopsy alone is not sufficient to detect PCa, compared with systematic biopsy.

Introduction

Prostate cancer (PCa) rarely causes symptoms unless it is advanced. Thus, suspicion of PCa resulting in a recommendation for prostatic biopsy is most often raised by abnormalities found on digital rectal examination (DRE) or by elevated serum prostate-specific antigen (PSA). Transrectal ultrasound (TRUS) guided systematic biopsy (TRUS-SB) is the most commonly used method when there is suspicion of PCa. However, the question of how often a prostate biopsy will turn out to be false-negative is of clinical as well as statistical importance. Daneshgari et al. reported a 25% chance of missing a PCa using systematic biopsy after examining 112 patients and in which 91 with PCa.[1] Rabbani et al. came to a similar finding that 23% of the 118 patients were failed to identify PCa using the same methodology.[2] Thus, various biopsy strategies have been devised to increase the diagnostic yield of prostate biopsy. Magnetic-resonance imaging (MRI)-guided biopsy is applied in clinical practice. However, MRI-guided biopsy is cost-consuming and time-consuming, which does not fit all patients, especially those with implant, pacemaker, or claustrophobia.[3] Color Doppler ultrasonography (CDUS) is one of the tools to increase PCa detection rate,[4] owing to the relationship between angiogenesis and tumor growth.[5] CDUS interprets the blood velocity and direction by the different frequency shift of US waves and removing nonvascular artifacts by wall filtering.[6] However, very low speed vessels might also be dropped if the wall filter setting is too high. That is to say CDUS is poor at microvascular with identifying lower blood flow speed. That might cause a decreased sensitivity in distinguishing less advanced PCa. Superb microvascular imaging (SMI) is considered the next generation of CDUS. It shows the ability of demonstrating very low blood flow signals with less artifacts, applying a multidimensional filter.[7] That might give a hint that SMI can provide more detailed vascular signals in correlation with PCa. Researchers came up with a significant positive link between microvascularity and PCa back to 1993.[8] More experiment results demonstrated the feasibility of adding the blood flow information in predicting potential malignancy.[9,10]

Besides the interpretation of vascularity, tissue stiffness is also an important factor in predicting malignancy. Previous research tried to figure out the tissue stiffness between benign and malignant lesions using strain elastography ultrasound (EU).[11,12] A better understanding of tissue properties and their distribution in the prostate might increase the accuracy of targeting for tissue acquisition and eventually improve the PCa detection.

However, limited attention has been paid to the application of SMI guided targeted biopsy (SMI-TB) and elastography ultrasound-guided targeted biopsy (EU-TB) in detecting PCa. To our best knowledge, no study of distinguishing PCa by comparing these 3 methods (TRUS-SB, SMI-TB and EU-TB) has been documented. Consequently, the present study was aimed to evaluate which property can better differentiate PCa tissue from normal tissue, and we prospectively evaluated SMI and EU as guides for TB to evaluate which is more useful in increasing PCa detection when performed before a conventional TRUS-guided systematic biopsy.

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