More data on the use of mapping biopsies

There is no doubt that transperineal, template-guided mapping biopsies (TTMBs) can find prostate cancer where more traditional 8- or 12-core transrectal ultrasound (TRUS)-guided biopsies often don’t.

New data reported by Taira et al. provide further guidance on the outcomes of TTMBs in 373 patients undergoing TTMBs for repeat and initial biopsies between January 2005 and September 2008 (79 as an initial biopsy and 294 after ≥ 1 prior negative biopsy).

The results of this study showed that:

  • Cancer detection in men having a TTMB as an initial biopsy was 75.9 percent.
  • For men who had had 1, 2, and ≥ 3 prior negative biopsies, cancer detection rates were 55.5, 41.7, and 34.4 percent, respectively.
  • In all, 55.5% of the cancers identified had a Gleason score of ≥ 7.
  • The majority of the cancers were multifocal.
  • There was no significant change in the number of positive biopsy cores or the patients’ Gleason scores as the number of prior biopsies increased.
  • The anterior and apical aspects of the prostate were among the most common cancer locations.

The authors conclude that TTMB is able to offer a high rate of cancer detection when used for initial and repeat biopsies, and that this technique is “particularly effective at diagnosing anterior and apical cancer.”

The unanswered question posed by this paper is, of course, how many of the tumors identified using TTMB and other mapping biopsy techniques are in fact clinically significant in the case of the individual patient? A Gleason 3 + 4 = 7 cancer in a patient with a slowly rising PSA that has gone from 3.2 to 5.4 over (say) 4 years may be of almost no clinical relevance whatsoever in a 74-year-old, and of dubious relevance in a 64-year-old. Just because it is possible to find such tumors using mapping biopsies doesn’t necessarily make this a good idea. And the shorter the life expectancy of the patient, the less the likely importance of finding such tumors and treating them.

    3 Responses

    1. To me the most important question is whether or not the Gleason score was more accurately predicted with these types of biopsies. There is little doubt that you will find prostate cancer in most men of [over 50 by using mapping biopsies]. The question is are they better predictors of final pathologies after radical prostatectomy.

    2. What strikes me as interesting and significant is the fact that the majority of the cancers were multi-focal even in these “hard to find” tumors. This further encourages questions, in my mind, as to whether the already debatable “focal” treatment can ever reach the success rates realized by the more traditional radical forms. Of course, only time will tell. – (aka) az4peaks

    3. I’m with Chris, you hope that a mapping biopsy will give you the right Gleason score. From what I’ve read on this board, standard 12 needle TRUS biopsy undergrades about about a third of the time.

      John makes a good point as well. I went from a 51 needle mapping biopsy that only found two small (10% areas) of Gleason 6 cancer on one side to focal cryo treatment of those areas. The follow-up TRUS biopsy found two more small (10 and 15%) areas of Gleason 6 on the same side. Apparently, I’ve got a number of very small foci of cancer (1-3 mm) on that side that fit through the mapping grid. More biopsies will just find different small cancers. Since the doctors performing focal cryo continue to report a 90% success rate, I’ve got to assume that I’m more “multifocal” than most.

      Mike’s comments are good to consider too. I’ve gone back to an active surveillance program for now, but with longevity calculators saying (at age 61) that I’ve got 30 more years, I may consider a nerve-sparing freeze of the entire right side if I don’t like what PSA and the next biopsy say. With cryo, retreatment is an option, but treating a larger area will involve a greater chance of side effects.

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