False-negative findings on mpMRI scans of men with clinically significant prostate cancer

Some people aren’t going to be happy about the following data, but they come from one of the most sophisticated prostate cancer imaging centers in the world … and they make it very clear indeed that multiparametric MRI scanning (mpMRI) is less than perfect in identification of risk for prostate cancer.

The paper by Borofsky et al. comes from researchers involved with three groups at the Clinical Center of the National Cancer Institute in Bethesda, Maryland, and with the full participation of Dr. Choyke and his colleagues at the Molecular Imaging Program there.

The goal was to try to characterize clinically important prostate cancers that were not identified after mpMRI scans of 100 consecutive patients who all went on to have a radical prostatectomy.

  • 162 prostate cancer lesions were identified pathologically (by an experienced GU oncologist who knew nothing about the MRI results).
  • 80 of these lesions were considered to be clinically unimportant (< 5 mm, Gleason score 3 + 3)
  • 136/162 lesions (84 percent) were correctly identified on mpMRI (by experienced uroradiologists who knew nothing about the pathology results)
  • The sizes of 8/162 lesions (5 percent) were underestimated on mpMRI.
  • Of the 26/162 lesions (16 percent) not identified on mpMRI
    • 17 were Gleason 3 + 4 = 7
    • 1 was Gleason 4 + 3 = 7
    • 7 were Gleason 4 + 4 = 7
    • 1 was Gleason 4 + 5 = 9
  • Of the same 26 lesions not originally identified on mpMRI
    • 8 were retrospectively assigned a PI-RADS score of 1
    • 7 were retrospectively assigned a PI-RADS score of 2
    • 6 were retrospectively assigned a PI-RADS score of 3
    • 5 were retrospectively assigned a PI-RADS score of 4
  • On a per-patient basis, based on the information about the 100 consecutive patients
    • mpMRI detected clinically important prostate cancer in 99/100 patients (99 percent)
    • At least one clinically important lesion was missed in 26/100 patients (26 percent)
    • Prostate cancer lesion size was underestimated in 8/100 patients (8 percent)

Borofsky et al. conclude that:

Clinically important lesions can be missed or their size can be underestimated [on mpMRI]. Of missed lesions, 58 percent were not seen or were characterized as benign findings at second-look analysis. Recognition of the limitations of [mpMRI] is important, and new approaches to reduce this false-negative rate are needed.

However, this doesn’t mean that mpMRI isn’t valuable. It is. And more so in some patients than in others.

The point that Borofsky et al. are making is that mpMRI is not perfect. Even they missed all lesions in one patient entirely. Thus the exclusive use of mpMRI-guided biopsies are also not perfect. Men (and their doctors) who think they can do without a systematic biopsy as part of the diagnosis of prostate cancer are deluding themselves. Some patients will get missed by  by the use of only mpMRI-guided biopsy.

We are much better at accurately identifying most cases of clinically significant prostate cancer than we werer a decade ago … but we still have a ways to go before we can reliably claim to be able to accurately identify “all” prostate cancer lesions in “all” patients with clinically signifciant prostate cancer and then treat those patients appropriately.

2 Responses

  1. Thanks for sharing these important findings.

    The take-home message for me is that any individual imaging study might provide an incomplete description of a patient’s clinical status. However, by using the results of multiple scans spaced properly over time, it is possible to get a pretty good indication of how a patient’s tumor(s) are changing over time.

    Together with a careful analysis of corresponding changes in PSA kinetics, this makes it possible to practice evidence-based treatment for each person whereby hypotheses regarding presumed mechanisms responsible for cancer progression are tested scientifically by subjecting them to falsification. This is the promise of genomic, patient-centered medicine and it is coming closer to being realized as imaging technologies become more accurate and accessible.

  2. If I am reading this correctly, it says some but not all of the clinically significant prostate lesions were found in 99 out of 100 patients?

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: