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Geometry-- yes, geometry-- and prostate cancer???????

Something occurred to me, and I'd like the input of rational, imaginative people to tell me if it makes any sense or not.

Two things seem clear: 1) statistics show that a trans-perineal biopsy is safer than a trans-rectal one simply because the former avoids an area rife with potentially dangerous bacteria and 2) an mpMRI-guided fusion biopsy (with the MRI images being fused with the real-time Ultra Sound) allows quite accurate targeting of suspicious lesions and is vastly superior to a blind Ultra Sound.

And yet, we rarely if ever hear of trans-perineal mpMRI-guided fusion biopsies. Why? Could it be that the geometry of inserting the biopsy needle through the perineum greatly limits the areas of the prostate that are accessible and significantly lessens the cancer-detecting ability of the fusion biopsy?

I have no idea if any readers of this post will 'know' the answer to my question. But I would certainly welcome informed speculation!

  1. I have something important to add to the foregoing, after speaking to a Physician's Assistant to a Urologist who does frequent prostate biopsies. She told me that although it is true that trans-perineal biopsies are far safer than trans-rectal ones in terms of avoiding infection following the biopsy, the reason they have not supplanted the trans-rectal biopsies is, evidently, convenience (whether for the physician or the patient, I'm not sure). The physician's assistant told me that trans-perineal biopsies require sedation of the patient, simply because it is too painful to undergo without it. The skin of the perineum apparently has many more nerve endings than the interior of the rectum, making the repeated insertion of a needle in the former an untenable proposition.

    And, incidentally, she said that the prostate was equally accessible through the perineum as through the rectum, so if you are willing to undergo sedation in order to greatly reduce the possibility of infection, you will have just as good a biopsy of your prostate.

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