Accuracy of Multiparametric Magnetic Resonance Imaging for Extracapsular Extension of Prostate Cancer in Community Practice. - Beyond the Abstract

Recently, multiparametric MRI (mp-MRI) has become a popular pre-prostatectomy imaging modality for men diagnosed with prostate cancer (PCa).  With the increased use of mp-MRI, the MRI/TRUS fusion biopsy has also been advocated as a diagnostic tool for the detection of prostate cancer. Unfortunately, the same limitations for mp-MRI are inherent in the MRI/TRUS fusion biopsy in a community practice setting. 

In the preoperative setting, mp-MRI attempts to predict extracapsular extension (ECE) or seminal vesicle invasion (SVI) of prostate cancer and may influence the surgeon’s decision to perform a nerve-sparing approach. Currently, the sensitivities reported from large academic institutions range from 43 to 75% with the presence of dedicated genitourinary radiologists[1, 2]. 

In a private practice setting, however, our study demonstrated a substantially lower sensitivity rate for mp-MRI to detect ECE. A complete pathologic analysis of ECE illustrated a sensitivity of 12.5% of mp-MRI to correctly identify ECE in our institution. This poor sensitivity of mp-MRI in the community could be attributed to the varying degrees of experience in radiologists reading prostate MRIs. In these community radiology groups, it is likely that the sheer volume of prostate MRIs is much lower than the number found in large academic centers and that the images are interpreted by radiologists without genitourinary fellowship training. Therefore, it is with this in mind that we are hesitant to adopt mp-MRI as a routine preoperative tool in patients with localized prostate cancer. 

Similarly, the growing popularity of MRI/TRUS fusion biopsy in non-academic centers cannot be substantiated by evidence. While it is reported that MRI/TRUS fusion biopsy tends to be superior to mp-MRI in identifying ECE in patients with prostate cancer, it should be noted that the radiologists assisting in the MRI/TRUS fusion biopsy had extensive prostate MRI experience, with 7 and 15 years respectively[3]. In a study by Ma et al., MRI/TRUS fusion biopsy was used in conjunction with a standard sextant biopsy and found an increased detection of Gleason ≥7 prostate cancer. However, this study is difficult to apply to the community setting as the images were interpreted by highly specialized radiologists with a minimum of three years’ experience with prostate MRI [4]. 

Despite promising results, it is premature to accept both mp-MRI and MRI/TRUS fusion biopsies as routine preoperative imaging as the findings from large academic centers cannot be translated to community clinical practice. With varying degrees of experience in radiologists and the lack of highly specialized radiologists, it is likely that the sensitivity of both mp-MRI and MRI/TRUS fusion biopsies in the community will not meet the diagnostic imaging standards found in academic centers. Therefore, at this point in time, caution must be exercised when accepting results of MRI/TRUS fusion biopsies as well as mp-MRIs performed in the community.

Written By: Rachel Davis, Amirali Salmasi, Christopher Koprowski, Sinae Kim, Young Suk Kwon, Izak Faiena, Neal Patel, Sammy E Elsamra, Isaac Yi Kim

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Reference:

  1. Bloch, B.N., et al., Prediction of prostate cancer extracapsular extension with high spatial resolution dynamic contrast-enhanced 3-T MRI. Eur Radiol, 2012. 22(10): p. 2201-10.
  2. Jeong, I.G., et al., Incremental value of magnetic resonance imaging for clinically high risk prostate cancer in 922 radical prostatectomies. J Urol, 2013. 190(6): p. 2054-60.
  3. Raskolnikov, D., et al., The Role of Magnetic Resonance Image Guided Prostate Biopsy in Stratifying Men for Risk of Extracapsular Extension at Radical Prostatectomy. J Urol, 2015. 194(1): p. 105-11.
  4. Ma, T.M., et al., The Role of Multiparametric Magnetic Resonance Imaging/Ultrasound Fusion Biopsy in Active Surveillance. Eur Urol, 2016.
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