(This new thread stems from the following thread to give a more detailed reply to the question quoted. I hope others will contribute if they know more about this question. Jim)
Re: how many biopsies are taken before discovery of prostate cancer
Originally Posted by lenapeter
Jim - have you any figures on how much PCa is triggererd by DRE and biopsies?
I think a lot of us wonder about this, especially as we have biopsies performed.
My impression is that it is not a problem with DREs, though some procedures like the PCA3 Plus test and its predecessor the uPM3 test use a vigorous DRE to deliberately cause shedding of some prostate cells into the urine. Perhaps some go to the blood as well, but it is probably an extremely small risk, and I can't find any research linking DREs to spread.
There have been studies done about whether biopsy causes any spread of prostate cancer cells, and I've heard several audience questions to experts about this at conferences. My impression is that biopsy does cause some spread of prostate cancer cells, though it is not typcial, but that adverse impact is quite rare. In other words, even if there is spread of some cells, they are rarely viable and rarely cause any trouble.
"Iatrogenic" is a strange word that I never knew until I got into this world of prostate cancer. It basically means "doctor caused." I just went to the free Government web site [url]www.pubmed.gov[/url] and used this search string to check on relevant studies: " iatrogenic prostate cancer AND biopsy ". Here are some key facts from hit #14 (many of the rest looked irrelevant); it is highly technical, but the abstract excerpts quoted below are pretty clear:
Urology. 1997 Apr;49(4):515-20."Transrectal ultrasound -guided biopsy causes hematogenous dissemination [meaning spread in the blood] of prostate cells as determined by RT-PCR [RT-PCR: Reverse Transcription-Polymerase Chain Reaction, which is a valuable research tool; I can explain if desired.]." Moreno JG, O'Hara SM, Long JP, Veltri RW, Ning X, Alexander AA, Gomella LG. Department of Urology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA. "... OBJECTIVES: To determine if transrectal ultrasound-guided (TRUS) prostate biopsy causes dissemination of prostate cells into the circulation... RESULTS: Among the 47 TRUS cases, 43 specimens were evaluable. Forty-two cases were negative before biopsy; among these patients, 4 cases (9.5%) converted to a positive RT-PCR PSA result. Both benign and malignant TRUS biopsies were capable of producing a positive RT-PCR PSA signal implicating iatrogenic dissemination of cells. All three TURP cases converted from a negative to a highly intense positive signal. CONCLUSIONS: We conclude that a positive RT-PCR PSA signal may result from release of prostate cells into the peripheral circulation after a TRUS biopsy and TURP. TURP causes greater dissemination than TRUS.... This may be an important mechanism of prostate cancer dissemination meriting further investigations."
Here's another, later reference that PubMed highlighted as a paper related to hit #14:
Urology. 1998 Aug;52(2):261-6; discussion 266-7.Detection and clearance of prostate cells subsequent to ultrasound-guided needle biopsy as determined by multiplex nested reverse transcription polymerase chain reaction assay.Price DK, Clontz DR, Woodard WL 3rd, Kaufman JS
, Daniels JM, Stolzenberg SJ, Teigland CM.
Molecular Biology Laboratory, Cannon Research Center, Carolinas Medical Center, Charlotte, North Carolina 28232-2861, USA.
OBJECTIVES: To determine if circulating prostate cells are detectable subsequent to transrectal ultrasound (TRUS)-guided biopsy, and if so, whether cells remain in circulation for up to 4 weeks.... RESULTS: Of 45 patients with biopsy-proven adenocarcinoma, 22 were RT-PCR positive prebiopsy and all remained positive 30 minutes postbiopsy. Of 23 patients with adenocarcinoma who were RT-PCR negative prebiopsy, 5 (22%) converted to positive 30 minutes postbiopsy (P < 0.001). Four of these 5 patients returned to negative after 1 week or 1 month. Of 45 patients without cancer at biopsy, 32 were RT-PCR negative prebiopsy and 6 (19%) converted to positive 30 minutes postbiopsy (P < 0.001). Although four of six available samples were still positive at 1 week, all four samples available 1 month postbiopsy were negative. CONCLUSIONS: Detection of circulating prostate cells subsequent to biopsy occurred in 11 of 55 (20%) previously RT-PCR negative patients, a proportion twice that reported in the literature. We attribute this higher proportion to the simultaneous detection of PSA and PSM mRNA in our multiplex assay. Conversion rates were similar in patients regardless of biopsy result. Testing of serial postbiopsy blood demonstrates clearing of these cells by 4 weeks in most patients."
The last sentence is very
important. It is hard for cancer cells to take hold and establish themselves even if they have made it into the blood.
That means that spreading cancer due to a biopsy is apparently a rare event.
It does make you wonder if saturation biopsies, which can involve, say, 40 to even more than 100 needle sticks, might increase the odds, and whether many repeated biopsies would increase the odds.
By the way, I substituted "DRE" and "digital rectal exam" separately in the above PubMed search and got no hits; to me that indicates that no such published research has been done, though my search string may have not covered all the instances. Also, poster studies are presented at medical and medical research conventions that typically do not get picked up by PubMed, and it is possible that this question has been explored in a poster study.