Study explores viability of micro-ultrasound for prostate cancer detection

A study published in Radiology showed that micro-ultrasound yielded comparable detection rates for prostate cancer as multiparametric magnetic resonance imaging (mpMRI); however, while micro-ultrasound can facilitate real-time targeted biopsies, it was also significantly inferior to mpMRI in preventing biopsies.¹

In the prospective study of 94 men with suspected prostate cancer, researchers noted micro-ultrasound had a 35% detection rate for clinically significant prostate cancer (csPCa) in comparison to a 39% detection rate for mpMRI. The study authors also noted similar detection rates for clinically insignificant PCa (16% for micro-ultrasound vs. 15% for mpMRI) and cribriform and/or intraductal PCa (14% for micro-ultrasound vs. 15% for mpMRI), according to the study.

In comparison to conventional ultrasound, the researchers pointed out that micro-ultrasound has a fourfold higher crystal density along the transducer, which facilitates a threefold greater increase in spatial resolution.

They also found that slightly more than two-thirds (67%) of the mpMRI targets were visible on micro-ultrasound, which could allow targeted real-time biopsies. In related research, the study authors added that targeted biopsy findings revealed a similar incidence of csPCa, whether clinicians utilized micro-ultrasound or conventional transrectal ultrasound (TRUS).²

“This highlights the advantage of micro-ultrasound for targeted biopsy over MRI fusion-targeted biopsy coupled with conventional TRUS,” wrote study co-author Masoom Haider, BAM, MD, FRCPC, a professor within the Department of Medical Imaging at the University of Toronto and head of the Radiomics and Machine Learning Lab at Mount Sinai Hospital in Toronto, and colleagues.

However, the study authors acknowledged that micro-ultrasound was significantly less effective than mpMRI in preventing biopsy (10% compared to 34%).

“Micro-ultrasound lacks the functional assessment component of MRI (diffusion-weighted imaging and dynamic contrast-enhanced sequences) for the interrogation of suspicious sites based on morphologic features. That may be the primary reason for the higher number of false-positive lesions identified at micro-ultrasound than at mpMRI in our study,” noted Haider and colleagues.

While the addition of non-targeted systematic biopsy to MRI and micro-ultrasound targeted biopsy did not lead to increased detection of csPCa, Haider and colleagues said it did uncover nine additional cases of clinically insignificant prostate cancer. Previous research has demonstrated that the combination of non-targeted systematic biopsy and MRI-targeted biopsy increases the detection of csPCa and clinically insignificant prostate cancer, but Haider and colleagues point out that 898 non-targeted systematic biopsy cores could have been avoided in their study population of 94 men.

“Our study shows that the replacement of non-targeted systematic biopsy with micro-ultrasound-targeted biopsy may be a better alternative,” added Haider and colleagues.

While acknowledging the need for subsequent multicenter randomized trials, the study authors said the combination of MRI and micro-ultrasound could enhance the radiologist’s ability to detect prostate cancer.

“Our results show that micro-ultrasound is an attractive addition to multiparametric MRI in the detection of clinically significant prostate cancer and that both modalities complement each other,” noted Haider and colleagues.

In regard to study limitations, the researchers conceded that some cancers may have been undetected due to the lack of an optimal reference standard, such as transperineal template mapping biopsy, being utilized for the study. They also noted that obtaining two biopsy cores for lesions only identified on micro-ultrasound versus three biopsy cores for MRI-detected lesions and concordant targets may have lowered the detection rate of clinically significant prostate cancer for micro-ultrasound. Another limitation was having single operators review the mpMRI and micro-ultrasound images, according to the study authors.

References

1. Ghai S, Perlis N, Atallah C, et al. Comparison of micro-US and multiparametric MRI for prostate cancer detection in biopsy-native men. Radiology. 2022 Jul 19;212163. doi: 10:1148/radiol.212163. Online ahead of print.

2. Van de Ven WJM, Sedelaar JPM, van Der Leest MMG, et al. Visibility of prostate cancer on transrectal ultrasound during fusion with multiparametric magnetic resonance imaging for biopsy. Clin Imaging. 2016;40(4):745-50.