Prostate Biopsies

[mike999]

I have been told by my urologist that prostate biopsies have a "30 % false negative rate." that even though a biopsy does not detect evidence of cancer..there is a 30 % chance that cancer is still present. He said that the error rate is due to sampling variations...they only take a small sample of cores compared to the size of the prostate.

I would like to here from others regarding this statistic. It leaves me with little confidence in the biopsy as a diagnostic tool.

Thanks,

Mike

[IADT3since2000]

Hi Mike,

I've seen that 30% false negative statistic too.

Of course it depends on what it is based on: the kind of biopsy (old-style 6 core, newer 5 region (usually 12 core), "saturation" ranging from 15 to around 24, "3D mapping" with a sample every 5 mm throughout the prostate (that's definitely saturation, with an average per Dr. Onik's initial 110 patients of 46 sticks!), whether guided by TRUS (Trans Rectal UltraSound) or color Doppler TRUS (or neither!), the size of the prostate and BPH status, the nature of the cancer (such as cases caught early, late, all comers, varying in extent of cancer, shape and location), DRE status, PSA and PSA velocity, free PSA results, PCA3Plus results, previous biopsy or not, finasteride (and probably Avodart) use, and probably some other factors.

One study of the 3D Mapping saturation biopsy technique indicates 95% accuracy in detecting clinically significant cancers. While not as good, color Doppler TRUS guided biopsies should also achieve better results than 30% false negatives.

Do you want more detail on Dr. Onik's technique and results, with his comments on other types of biopsies? I've got the workbook with vugraphs from his talk at the International Conference on Prostate Cancer 2006, held in Reston, Virginia.

If you go to the Government site [url]www.pubmed.gov[/url], you can find studies that look at the issue of false negatives in prostate biopsies.

Jim

[mike999]

Thanks Jim....I had a recent biopsy where they took 16 cores covering a number of areas distributed over my prostate. All of the core samples were negative. The issue is my PSA & free psa #s ....my orig.psa was 6.7 which triggered the biopsy because of a nodule on my prostate. 3 months after the biopsy I had follow up psa tests in April
the tests were a week apart:
1st: psa was 6.6
2nd: psa was 11.3 & free psa was 15 %
3rd:

[mike999]

Thanks Jim:

I am concerned because I had a biopsy last Nov...they took 16 cores, they were all negative. {my psa was 6.7, & I have a nodule on my prostate.}

I had follow up psa tests in April with highly variable results:{the tests were ~ 1 week apart}

1st: psa 6.6
2nd: psa 11.4, free psa 15 %
3rd: psa 7.1, free psa 10 %
4th: psa 6.6, free psa 12 %


My urologist recommends another biopsy in the next 2 months. I went to my PC to review these results , he recommended that I wait 3 months & have the psa & free psa tests repeated again, based on the results we will discuss the need for another biopsy.

What do you think of this ? are my variable psa results indicative of cancer ?

Thanks,

Mike

[IADT3since2000]

Hi again Mike,

Please remember that I have had no enrolled medical education or medical experience; what I post is based on what I've interpreted from talks, written resources, advice from medical professionals and fellow survivors, and personal experience. I hope it will be useful to provide leads and things to think about and confirm for yourself.

I'll bet the variability means either something in the test procedure affected the result of 11.4 or something other than cancer was going on, like a short-term spike due to an underlying infection or other short-term cause, or a combination of non-cancer causes. That variability, prior to any treatment, is a sign of something other than cancer as I see it, though cancer could also be present and could account for those low free PSA readings. Cancer causes a consistent doubling of cells, leading to a consistent doubling of PSA. That's certainly not what your pattern looks like.

The other four tests are quite close (counting the original 6.7). Even the 7.1 result is less than 8% higher than the two 6.6 results, and I believe that is within the day-to-day variability often seen in PSA results. It has to be a favorable sign that your PSAs now, not counting the 11.4 result, are virtually the same (in fact slightly lower than) the 6.7 result three months earlier. Trend analysis is very important in assessing the possibility of prostate cancer, and you actually have a negative trend.

Do you know the story on the cores taken in the area of that nodule the urologist found? He must have taken cores in that suspicious area. What did he find? It should be in the record. Obviously it was not cancer, but was there something benign that explained the nodule?

Having 16 negative cores taken is a favorable sign, as that number is well above the norm. It makes sense to me that even if you have a tumor, it is probably small - small enough to be missed by the 16 probes.

Do you know how large your prostate is? The rule-of-thumb is that healthy prostate tissue will produce .066 PSA units for every cc of the gland (page F4 in the Primer).

Jim