What’s the best predictor of prostate cancer after a prior negative biopsy?

According to a recent prospective study from a group of Italian investigators, the answer to that question is, “Multiparametric magnetic resonance imaging” (mp-MRI). However, this needs to be confirmed in at least one other large, prospective study.

Porpiglia et al. enrolled 170 patients who had continuing and persistent indications of risk for prostate cancer after an initial negative systematic prostate biopsy. These 170 patients were then all subjected to a variety of further tests, including follow-up total PSA tests, a %free PSA test, the PCA3 test, the Prostate Health Index (phi) test, and an mp-MRI, after which they received a standard, systematic, repeat biopsy carried out by a urologist who was blinded to (i.e., not aware of) the results of the mp-MRI.

Porpiglia et al. were able to show that:

  • The most significant predictor of a positive repeat biopsy result was provided by mp-MRI.
  • On univariate analysis, the mp-MRI was significantly better at predicting a positive repeat biopsy result than the combination of the phi score + the PCA3 score (p < 0.001).
  • On the multivariate logistic regression analysis, only the mp-MRI was a significant independent predictor of prostate cancer diagnosis on repeat biopsy (p < 0.001).

If this set of results can be confirmed in a second high-quality study, this would tend to suggest that mp-MRI has a very real diagnostic value — at least in the diagnosis of men with one negative systematic biopsy and persistent indications of risk for prostate cancer, and perhaps especially if combined with MRI/TRUS-guided fusion biopsy methods.

2 Responses

  1. Medicine certainly has continued to improve on man’s ability to find smaller and smaller amounts of what we today call “prostate cancer.” Using methods available in the past, we already know that about 50% of men of 50 years of age are carrying around some form of prostate cancer (and many of those men will never know that they have it). That percentage increases roughly in line with age … 60% of 60-year-olds, etc.

    This report seems to reinforce that if we look even harder, we will probably find some even tinier “weird cells,” but are these the findings we are most interested in?

    To re-use a phrase, I think we are looking (spending scarce resources) in all the wrong places. Look, and you will find … and create a whole new class of “patients.”

  2. That is a good point, Casey, that as age increases so does the probability that a prostate cancer will be found.

    However, the reason we look is not just to find prostate cancer, but to determine if a prostate cancer is low grade or high grade, and the only way to do that today is through a biopsy. If that biopsy can be directed instead of blind it not only avoids unnecessary biopsies, but may also (with various technologies, including genetic testing of the tumor) determine whether the cancer needs treatment. At least, that is where I think the direction is going. Another point is that for MRI, color Doppler, and other imaging technologies, the tumor has to be a minimum size before it can be detected, so it could still miss a tumor of less than 4 mm in diameter.

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