Is shear wave elastography the shear wave of the future?

Just this morning, the University of Dundee issued a media release that included the following statement:

an ultrasound process called shear wave elastography (SWE) has been shown to offer much greater accuracy and reliability in diagnosis of prostate cancer, while being a non-invasive and cheaper method than those currently used.

Apparently The Guardian — a newspaper in the UK — had managed to get hold of an early copy of the University of Dundee’s media release. On Sunday they published this article, which appears to be lifted directly from the information in the media release.

We learned about the article in The Guardian from a reader in the UK.

And so we had a problem. … There is no reference in either the media release or the article in The Guardian to the scientific research on which the information and the claims in the media release are based.

We have known for years that elastography had the potential to be used to assess risk for prostate cancer. This is by no means new knowledge. Thus it is hardly surprising that some form of ultrasound process that involves SWE can be used to visualize cancer and other forms of abnormality in the prostate. It also comes as no surprise that it can do this better than standard “gray-scale” transrectal ultrasound (TRUS).

Let’s be very clear. … A new, accurate system for imaging of the prostate that could allow improved estimation of clinical risk would be a wonderful thing. Such a system would need to be able to reliably identify prostate cancer tissue in living patients with higher selectivity and specificity (two measures of “accuracy” normally assessed for any type of test) than not just old-fashioned “gray-scale” TRUS but other forms of currently available imaging too. If it actually turned out to be no more expensive than current forms of “gray-scale” TRUS, then that would make it even more desirable. However, …

The claim that SWE meets not just these criteria but that it can actually be used to diagnose prostate cancer with a high level of accuracy (as opposed to identify risk for prostate cancer with a higher level of probability) needs to be clearly proven — preferably in prospective clinical trials — before anyone should take this sort of claim very seriously.

Are there any such data?  Apparently there may be. There is an article by Wei et al. from the team at the University of Dundee that is currently in press in the Journal of Urology. It is entitled, “Performance characteristics of transrectal shear wave elastography (SWE) imaging in the evaluation of clinically localised prostate cancer: a prospective study.”

According to the abstract of this paper (we can’t see the full text),

This was a prospective protocol-driven diagnostic accuracy study. 212 consecutive men undergoing laparoscopic radical prostatectomy (LRP) for clinically localised PCa were recruited into the study. Quantitative stiffness data of the prostate gland was obtained in each patient using an endocavitary transrectal transducer before LRP and compared with detailed histopathological examination of radical prostatectomy specimen using 3-D printing mold based technology ensuring improved image-histology orientation.

The results include the following:

Quantitative stiffness data estimated in kilopascals (kPa) was significantly higher in malignant compared with benign areas. With a cut-off value of 82.6 kPa, sensitivity and specificity of SWE were 96.8% and 67.8%, respectively (p < 0.01). Significant differences were observed for different grades of cancer with Young’s moduli 91.6 kPa, 102.3 kPa and 131.8 kPa for low (Gleason score 6), intermediate (Gleason score 7) and high grade (Gleason score ≥ 8) PCa respectively (p<0.05). SWE also detected capsular breaches with significant prediction of PCa pathologic staging.

The authors note that:

Potential limitations include selection bias and study being single centre site.

They also go on to conclude that

Quantitative SWE via transrectal approach accurately detected cancer foci and showed significant differences between cancerous and benign tissue. Moreover, this technique can be used to reliably phenotype PCa aggressiveness.

Your sitemaster will be writing to the team at the University of Dundee to see if he can get a copy of the full text of this paper. However, let’s be very clear that others are going to need to be able to replicate results like this before people start to replace older “gray scale” TRUS systems with transrectal SWE imaging technology, and your sitemaster remains skeptical of the claim in the original press release that this technology will turn out be “cheaper than current detection techniques”.

There is also a lesson here for the public affairs personnel at the University of Dundee (and the editorial staff at The Guardian). When you make scientific announcements like this, please provide the source information in your media release and as at least a footnote to your article!

One Response

  1. Your sitemaster has already received a copy of the full text of the article by Wei et al., and is preparing further commentary. He suggests that all external comment on this article be reserved until after your sitemaster posts this further commentary, and so external comment on this initial set of commentary is closed.

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