mpMRIs, MRI/TRUS fusion-guided biopsies, and systematic biopsies in monitoring of men on active surveillance

A new article in the Journal of Urology has provided us with some initial insight into the value of multiparametric MRIs (mpMRIs) in monitoring progression of patients on active surveillance protocols.

It has been widely recognized, for such patients, that regular, serial mpMRIs, when followed, as necessary, by MRI/TRUS fusion-guided biopsies, may have greater value than regular, serial systematic biopsies. Why? Because multiple systematic biopsies over time are inherently associated with risk for infections and effects on erectile/sexual function. However, the actual performance of regular, serial mpMRIs in the evaluation of men on active surveillance has yet to be well evaluated.

Frye et al. set out to conduct a retrospective analysis of data collected between 2007 and 2015 from men with prostate cancer who had visible prostatic lesions on mpMRI and who were being managed on active surveillance by staff at the NCI Clinical Center in Bethesda, MD. They included all patients who were being monitored with mpMRIs and who both received MRI/TRUS fusion-guided biopsies and systematic 12-core biopsies indicated by changes in the mpMRI data over time.

Progressive disease was defined by upgrading from ISUP Grade Group 1 to Grade Group 2, and by upgrading from ISUP Grade Group 2 to Grade Group 3.

Here is the summary of the findings:

  • The study included 166 patients on active surveillance who were given two or more MRI/TRUS fusion-guided biopsies.
  • The average (mean) patient follow-up was 25.5 months.
  • 49/166 patients (29.5 percent) were found to have had a pathologic progression.
    • Targeted, MRI/TRUS fusion-guided biopsies alone identified 22/49 patients (44.9 percent) of patients that progressed.
    • Systematic 12-core biopsies alone identified 15/49 patients (30.6 percent) of patients who progressed
  • MRI/TRUS fusion-guided biopsies detected 26 percent more pathologic progression on surveillance biopsies compared to systematic 12-core bipsies.
  • Progression on mpMRI was the sole predictor of pathologic progression at surveillance biopsy (p = 0.013).
  • With regard to the detection of pathologic progression, mpMRI progression in the entire cohort had
    • A negative predictive value (NPV) of 81 percent
    • A positive predictive value (PPV) of 35percent
    • A sensitivity of 77.6 percent, and
    • A specificity of 40.5 percent

The authors conclude that progression as identified using mpMRIs

predicts the risk of pathologic progression and patients with stable [mpMRIs] have low rate of progression.

They also note that:

Incorporating [MRI/TRUS fusion-guided biopsies] in [active surveillance] nearly doubled our detection of pathologic progression compared to [12-core systematic biopsies].

What this initial study seems to show us is that — based on these data — mpMRI scanning has a high negative predictive value. In other words, if there is no sign of a change on mpMRIs over time, it is highly likely that there is no change to the grade of the cancer either. However, it is not a guarantee. And so repeat biopsies are almost certainly goijng to be a good idea for all patients. Unsurprisingly, the question of how frequent those repeat biopsies might need to be among men with no clear signal of a need for a repeat biopsy doesn’t seem to be answered by this study.

The study also seems to confirm, yet again, that even when one is biopsying a patient with the benefit of MRI/TRUS fusion guidance, the sensible thing is to take 12 systematic cores as well as the necessary number of MRI/TRUS fusion-guided and targeted cores in order to maximize the probability of identifying an upgraded cancer. Remember that an upgrade may not necessarily be an immediate signal for treatment — particularly in the case of older patients or patients with co-morbid conditions in whom the upgrade shows only a very small amount of Gleason pattern 4 tissue (i.e., from ISUP Grade Group 1 to ISUP Grade Group 2). Continued active surveillance may still be a wise choice for some of those patients.

One Response

  1. Interesting read. Thanks for sharing.

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