MRI data and genomic data are telling us different things about prostate cancer risk

A new paper just published on line in the journal PLoS One is entitled, “Association between a 17-gene genomic prostate score and a multi-parametric prostate MRI in men with low and intermediate risk prostate cancer (PCa)”.

This new paper by Leapman et al. provides us with a retrospective analysis of the risk assessment data of men in a cohort of 186 patients diagnosed as having low- or intermediate-risk prostate cancer. All patients were being managed at the prostate cancer clinic at the University of California, San Francisco, and they were all given an Oncotype DX Prostate Cancer test (which gives each patient a genomic prostate score or GPS). Of these 186 patients, 100 also received at 3 T multi-parametric MRI scan within 2 years of having their genomic test.

The study was intended to determine to what extent the data from the mpMRI and the GPS data were telling us the same (or different) things about the risk for individual patients for having indolent or more aggressive types of prostate cancer.

The entire paper is available on line for free for interested readers, so we are not going to get into all of the details. Suffice it to say that — particularly for the men with intermediate-risk disease — the two different tests seem to be giving us different types of risk data about this cohort of patients, which is probably what many of our readers would have suspected. The authors conclude that:

Although a statistically significant association was observed between GPS results and MRI scores, a wide range of GPS values were observed across imaging categories suggesting that mpMRI and genomic profiling may offer non-overlapping clinical insights.

There are limits to how much can be extracted from this study for a number of reasons that are addressed in detail in the full text of this paper, but here are some of the most important things that do seem to be very clear:

  • Average (mean) GPS scores differed between mpMRI categories of patients.
  • A broad range of GPS scores was observed in all mpMRI categories of patients.
  • Among the men with Gleason scores of 3 + 3  = 6, the average (mean) GPS scores were not significantly different among the mpMRI categories of patients.
  • Among the men with Gleason scores of 3 + 4 = 7, there were significant differences between the average (mean) GPS scores among the mpMRI categories of patients.

In other words, particularly for the men with favorable intermediate-risk prostate cancer, the GPS scores seem to be telling su something different about patient risk than the mpMRI data. And what we don’t know about these patients (yet) is what effect that information might be having on patients’ outcomes over time.

The truth is that, as yet, we really don’t know the relative value of genomic testing and MRI imaging in the assessment of risk for a newly diagnosed patient. It is likely that one test or the other may be more important in at least some patients, and both might be valuable in others. Furthermore, the current study provides information about just one of the several genomic tests that are now available, and so we have no idea whether there are subsets of patients whose risk might be best assessed using one particular type of genomic test compared to the others.

The probability is that it is going to take us another 5 to 10 years to work out how best to start to re-assess risk based on all the new tests that have already become available (let alone any other tests currently in development). In the meantime, for most patients, the combination of Gleason score, clinical stage, and PSA level remains as the best validated set of information available, but other tests like mpMRI scans and the different genomic test data may still be helpful.

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