Washout gradient in dynamic contrast-enhanced MRI is associated with tumor aggressiveness of prostate cancer, "Beyond the Abstract," by Shih-Chieh Jeff Chueh, MD, PhD, et al

BERKELEY, CA (UroToday.com) - With the recent NEJM radical prostatectomy versus observation paper (Wilt TJ et al., N Engl J Med 2012;367:203-13) implicating no survival benefit of surgery in comparison with watchful waiting for patients with low-risk prostate cancer, the significance of being able to define biological aggressive versus non-aggressive prostate cancer is becoming even more important. Our paper indicated that washout gradient in dynamic contrast-enhanced (DCE) MRI could be a part of the key to the biological aggressiveness of prostate cancer.

For future clinical applications, we are further working on the following questions:

We would like to see whether these DCE MRI parameters can further differentiate Gleason score (GS) 6, versus GS 7, versus GS 8-10 prostate cancers. The importance of doing so is to get better and finer clinical correlations with the biological behavior of the prostate cancer. On one hand, by improving the resolution and the signal-to-noise ratio of MRI images, we hope to find the corresponding parameter ranges for various GS tumors. On the other hand, since our case numbers are limited, we would like to look for international collaborations with other centers to incorporate the same test protocol and to combine the data together for more comprehensive statistical analysis. There might be certain criticism to our article: Since biopsy (pathology) is definitely needed to prove the existence of prostate cancer, and GS will be available from biopsy (pathology), why do we still need a washout gradient DCE MRI?

"Since our case numbers are limited, we would like to look for international collaborations with other centers to incorporate the same test protocol and to combine the data together for more comprehensive statistical analysis."

One of the answers to the above criticism is that it's not uncommon to have upgrading of radical prostatectomy specimen (e.g.: a GS 6 on biopsy, but the final pathology became GS 7 or even 8), because of the random characteristics of prostate biopsy. This might might provide wrong information for the definitive treatment plan, especially for those patients undergoing active surveillance, brachytherapy, radiotherapy, or cryotherapy, because there would be no final surgical pathology to compare with. Because DCE MRI provides a panoramic view of the whole prostate, incorporating its information into a 3-dimension prostate biopsy protocol will very likely improve the ability to detect the most aggressive tumor in the whole gland, and thus would direct a more accurate therapy planning.

And the results of DCE MRI will also offer valuable information in tailoring the planes of surgical treatment. Whether to preserve the neurovascular bundles (NVBs) or not during radical prostatectomy or cryotherapy can depend on how close the MRI-detected tumors are located in relation to the NVBs. Additionally, determination of how aggressive the surgical excision at varying section margins needs to be (like apex and bladder neck) can also rely on the proximity of MRI-detected tumors at those spots. Even with the magnification provided by the most advanced robotic–assisted laparoscopic radical prostatectomy, human eyes (or hands in open surgery) still cannot identify microscopic prostate cancer cells. The use of DCE MRI might further decrease the positive surgical margin rates during radical prostate surgery.

A provocative thought is with our prior publication of high sensitivity (97%), specificity (98%), and negative predictive rate (99%) of combing the trace apparent diffusion coefficient (tADC) threshold and the nodular size threshold of diffusion tensor imaging (DTI) MRI to predict prostate biopsy results (Chen et al., J Magn Reson Imaging. 2011 Feb;33(2):356-63.), we might be able to avoid unnecessary prostate biopsy, which carries certain surgical risks itself; and to use both DTI and DCE data to guide the biopsy among those patients who possess high cancer likelihood for the best pathological yield. In that sense, DTI and DCE MRI information would be more valuable than PSA and digital examination (currently most commonly used parameters by practicing urologists) in deciding whether patients need biopsy or not, and help to get the most aggressive tumor part during the biopsy.

Additional reply to that criticism is somehow speculative, and will not be answered unless a long-term large investigational cohort of prostate cancer patients with their survival data and both DCE MRI and GS data available for comparisons: Will DCE MRI data be even better than GS in predicting prostate cancer survival? And will DCE MRI data provide more or even complementary information than GS in predicting prostate cancer progression?

Written by:

Shih-Chieh Jeff Chueh,* Yu-Jen Chen, Wen-Yih Isaac Tseng, Yeong-Shiau Pu, Chia-Tung Shun, and Woei-Chyn Chu as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.

*Department of Urology
National Taiwan University Hospital
Taipei, Taiwan

Washout gradient in dynamic contrast-enhanced MRI is associated with tumor aggressiveness of prostate cancer - Abstract

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