MRI scanning as a screening test for prostate cancer: data from a pilot study

A newly published study from the Sunnybrook group at the University of Toronto has investigated the possibility of MRI scanning as a method to screen men for risk of clinically significant prostate cancer.

Nam et al. recruited 47 unselected men of 50 to 75 years of age from the general population in the Toronto area. These men had never had a biopsy and had no known family history of prostate cancer. All 47 men were given a rectal examination (DRE), a standard PSA test, a 3-T multiparametric MRI, and a prostate biopsy. Men with no sign of prostate cancer on MRI were given only a 12-core systematic biopsy. Men showing evidence of possible prostate cancer on MRI were given both a 12-core systematic biopsy and targeted biopsies of areas shown to be suspicious for prostate cancer on MRI.

The research team found that:

  • 18/47 patients (38 percent) had prostate cancer.
  • 29/47 patients (62 percent) had no evidence of prostate cancer.
  • Prostate abnormalities were detected on DRE among 5/47 patients (11 percent).
  • The MRI score was
    • 1 in 6/47 men (13 percent)
    • 2 in 15/47 men (32 percent)
    • 3 in 9/47 men (19 percent)
    • 4 in 7/47 men (15 percent)
    • 5 in 10/47 men (21 percent)
  • Patients with an MRI score of 4 or 5 were considered to be at significant risk for prostate cancer prior to biopsy.
  • Gleason scores were
    • 6 in 6/18 positive patients (33 percent)
    • 7 in 8/18 positive patients (44 percent)
    • 9 in 4/18 positive patients (22 percent)
  • On biopsy there was evidence of cancer in
    • 15 patients on systematic biopsies
    • 3 patients who had targeted biopsies only
  • On multivariate analysis the patients’ MRI scores were better predictors of a prostate cancer diagnosis than their PSA levels.
  • The adjusted odds ratios (aORs) for diagnosis of prostate cancer were
    • 2.7 for MRI score
    • 1.1 for PSA level
  • The aORs for diagnosis of prostate cancer of Gleason score ≥ 7 were
    • 3.5 for MRI score
    • 1.0 for PSA level

Nam et al. concluded that prostate cancer screening using multiparametric prostate MRI scanning “is feasible for use in the general population.” However, they acknowledge that, at present, the lack of widespread availability of the relevant technology, and the potential cost factors, would make the application of such methodology to the general population difficult or impossible, and they limit themselves to calling for further research into the potential of MRI scanning as a screening technology at this time.

5 Responses

  1. I would suggest a change of wording. You say that on biopsy there was evidence of cancer in “3 patients who had targeted biopsies only”. I think that should be changed to “3 patients whose cancer was detected on targeted biopsies only”. Since all patients had systematic as well as possible targeted biopsies, there were not any patients who had targeted biopsies only.

    The overall detection rate of 38% strikes me as surprisingly high. These men were recruited by a newspaper ad. Granted, some might have responded because they were concerned about a high PSA result, but nevertheless the median PSA among the tested men was only 3.03 ng/mL, and 9 of the 18 detected cancers were in men with PSA < 4.0.

  2. Wow. Seems like one thing to sign up for an MRI for a research study, quite another to sign up for a prostate biopsy.

  3. It would appear that nine men had targeted biopsies based on MRI. But the targeted biopsies showed only three positive. Wonder if any of the other six were included in the 15 positive from the systematic biopsies?

  4. The 38% prevalence figure is interesting since it is approaching the prevalence seen in post-mortem studies of gerontological samples from the elderly population. Agree with Clara that it’s surprising the researchers persuaded this number of men to volunteer for a study involving a biopsy, certainly not representative of the general population of older men.

  5. Cliff:

    Please note that all the patients were given a systematic biopsy. A subset of the patients received a targeted biopsy too. So for the 3/9 men who had a positive biopsy based on having had a targeted biopsy we do known that that positive result came from the targeted biopsy.

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