Prostate cancer risk models and image-targeted biopsies


A new article in European Urology has pointed out that one is not going to be able to apply prognostic risk models (like the Kattan pre-treatment nomogram) to men who are diagnosed with localized prostate cancer based on techniques like MRI-guided biopsies.

In this article by Robertson et al., the authors show that (based on their data):

  • The standard, systematic, 12-core, transrectal ultrasound (TRUS)-guided biopsy
    • Reported about 11 percent of biopsy cores as positive.
    • Reported a mean maximum cancer core length of 4.3 mm.
    • Classified about 24 percent of clinically significant prostate cancers as being high risk.
  • By comparison, a 4-core, image-guided, transperineal, targeted biopsy
    • Reported about 44 percent of biopsy cores as positive.
    • Reported a mean maximum cancer core length of 7.8 mm.
    • Classified about 74 percent of clinically significant prostate cancers as being high risk.

The authors argue (accurately in our opinion) that, “Targeted biopsy strategies will require new risk stratification models that account for the increased likelihood of sampling the tumor.”

8 Responses

  1. So, does this article suggest that MRI guided biopsies are more accurate? What percent of MRI biopsies are currently used in the US?

  2. I don’t think there are enough prospective data yet to suggest the such biopsies are clinically more effective. They may well be more accurate when there is cancer that is visible within the prostate when certain types of MRI scan are employed, but in other cases (where the tumors are too small to be visible) a targeted biopsy wouldn’t be appropriate.

    The cost factor would potentially be enormous if every patient were to be given MRI-guided, targeted biopsies.

  3. Endorectal coil-based MRI-guided biopsies can be particularly useful in discovering cancers located in the anterior portion of the gland which may not be discoverable under normal biopsy procedures. … If the patient’s PSA is high and the doubling time appropriate then the endorectal coil MRI is particularly useful.

  4. Putting aside the “societal cost” issues if everyone were to do it — which are important but which no individual patient can be expected to care about in his own case — why would a patient not want an MRI-guided (or color-doppler guided) biopsy rather than a traditional TRUS biopsy? It might be more accurate. It is certainly not any less accurate. So why not?

  5. Jonathon:

    I can only answer a question like that with a comparable question:

    Putting aside the “societal cost” issues if everyone were to buy a Lamborghini — which are important but which no individual man can be expected to care about in his own case — why would a man not want a Lamborghini rather than a Kia or a Ford Escort? It would probably be more more fun. It is certainly faster. So why not?

    However, it isn’t that simple. There is a massive, potential societal cost. That cost would have to be paid by you … in your taxes. Of course anyone who is rich enough to pay for an MRI-guided biopsy himself is utterly entitled to do this (whether it makes a jot of difference to his diagnosis and treatment or not). He can also buy himself a Lamborghini to drive himself to the biopsy if he wants to.

  6. Sitemaster —

    Although I am not certain, it seems to me you are saying one of two things (or maybe both): (1) that people should consider the “societal” cost “if everyone did it” in making their own individual health care decisions, and/or (2) there is no credible evidence that MRI-guided (or color-doppler guided) biopsies are more accurate or otherwise better than “regular” TRUS biopsies.

    To the extent you are making the first point, I just don’t think it is reasonable to expect an individual to make his own medical decisions based on what the “societal cost” would be if everyone were to do it. With an important (potentially “life or dealth”) matter, people can reasonably be expected to seek the best health care that their insurers (government or otherwise) are willing to pay for — or that they individually can pay for — regardless of what would happen “if everyone did it.” (Public policy professors can sit in their ivory towers and debate social cost, but I want the best I can get).

    To the extent you are saying it is a waste of money because there is no credible evidence that MRI-guided (or color doppler guided) biopsies are more accurate or otherwise better than regular biopsies, that is certainly of interest. Becuase although I want the best health care I can get, I have no interest in throwing money away on something that is in fact not useful, or no better than the cheaper thing.

    So I guess what I would want is to ask a knowledgeable doctor, who feels that, when he is advising me, his sole duty is to me, this question: “Assuming money is no object, am I better off with a regular TRUS biopsy or a MRI-guided or color doppler biopsy?”

  7. Dear Jonathon:

    Actually I am absolutely not saying either of the two things you suggest. You are “putting words in my mouth.”

    All that I am saying is that there is a societal cost and that there is not sufficient evidence yet to draw the conclusion that every man suspected of prostate cancer should undergo an MRI-guided biopsy. What people want to do about this is an entirely personal decision, but I certainly don’t expect many of the organizations that provide health insurance coverage to necessarily agree that they should cover the costs of an MRI-guided biopsy at this time. To that extent, if you (or anyone else) wants to cover the cost themselves, you have the right to do so.

    I would also point out that your “knowledgeable doctor” has a conflict of interest when he advises you if he advises you to have any test (or treatment) that he gets paid for providing. This has long been one of the biggest problems related to the diagnosis and treatment of prostate cancer (and a bunch of other disorders too). I am not, however, suggesting that the advice proffered is necessarily right or wrong, only that the conflict of interests exists and that it may be affecting his or her judgment.

  8. The statement, ‘I would also point out that your “knowledgeable doctor” has a conflict of interest when he advises you if he advises you to have any test (or treatment) that he gets paid for providing. This has long been one of the biggest problems related to the diagnosis and treatment of prostate cancer (and a bunch of other disorders too)’ is truly the understatment. At what point in time is the medical industry self-policing?

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