Uh oh. All is not well in the world of prostate biopsy. The majority of needle biopsies for suspected prostate cancer (PCa) are performed by urologists using transrectal ultrasound (TRUS) guidance. This has been the conventional approach used for decades, but over time the number of needles used increased. Starting in the late 1980s, the standard protocol was called a sextant biopsy because it used 6 needles (3 on each side of the gland. In 1997, Norberg et al. published an article noting that sextant biopsies missed 15% of prostate cancers that would be picked up by using 8-10 needles.i However, it turned out that even that was not enough.
Within 10 years, the use of 12 needles had become the gold standard but according to Presti (2007), “…even with this approach there is a possibility of undersampling the apex of the prostate.”ii In fact, in 2016 a team from the Mayo Clinic wrote that the actual PCa detection of initial 12 core biopsies for “…yields cancer detection rates between 30–55%. The false negative rate for this 12 core schema is on the order of 20–24% and repeated 12 core or saturation biopsies show detection rates of 11–47%.”iii Inevitably, data like this led many urologists to bump up the number of needles to 14, 16, and even 24.
Increasing rates of post-biopsy infections
A new study by Shoag, et al. (2019)iv explore the current landscape of post-biopsy infections. Using SEER-Medicare linked records from 2001-15 for 30-day infection rates plus emergency department, hospital and ICU admissions, they ascertained that infections increased during the years 2001 to 2007 from 5.9% to 7.2%. This is roughly the same period in which sextant biopsies were abandoned in favor of 8, 10 or 12 needle biopsies, so it does not seem surprising that there were more infections despite advances in prevention and antibiotic use. After 2007, the rate stabilized through 2015, so that’s good news.
However, the Shoag study contains bad news: “… post-biopsy emergency room visits rose from 0.2% to 0.5%, … hospitalizations rose from 0.5% to 1.3%, … and intensive care unit admissions increased from 0.1% to 0.3%.” (They note that doctors who perform 25 or more biopsies per year have lower infection rates than doctors who do only 1 or 2 per year, implying that experience helps.)
The source of infection in TRUS-guided biopsies is the transfer of rectal/bowel bacteria into the prostate, prostatic urethra, and abdominal cavity through the rectal wall. The increase in the rate is believed to be due to both under-utilized pre-biopsy rectal swab and culture, and the growing number of patients who carry bacteria that is resistant to the ciproflaxin drugs that used to effectively prevent infection; and infection-related complications use medical dollars to the tune of $4,129 (average treatment cost).
In-bore MRI-targeted biopsies
At our Center, we offer real time, in-bore MRI-guided targeted biopsy. When a suspicious area of the prostate is revealed by our multiparametric MRI scan, we can strategically direct a minimum number of needles precisely into that area. This optimizes diagnostic accuracy. Studies in which MRI-targeted biopsies done in the bore of the magnet are compared with standard 12-core TRUS biopsies improve the detection of overall PCa as well as significant PCa.
A value-added advantage is the reduced risk of post-biopsy infections. Of course, we take great preventive precautions, but the use of significantly fewer needles helps minimize infection risk.
Men whose rising PSA raises fear of prostate cancer do not need another worry adding to their anxiety. In a world where mutating viruses and bacteria are quite concerning, we are doing our part to avoid exposing men to increased risk of infection after prostate biopsy.
iNorberg M, Egevad L, Holmberg L, Sparén P et al. The sextant protocol for ultrasound-guided core biopsies of the prostate underestimates the presence of cancer. Urology. 1997 Oct;50(4):562-6.
iiPresti JC Jr. Prostate Biopsy: Current Status and Limitations. Rev Urol. 2007 Summer; 9(3): 93–98.
iiiWoodrum DA, Kawashima A, Gorny KR, Mynderse LA. Targeted Prostate Biopsy and MR Guided Therapy for Prostate Cancer. Abdom Radiol (NY). 2016 May; 41(5): 877–888.
ivShoag JE, Gaffney C, Pantuck M, Sun T et al. Risk factors for infection after prostate biopsy in the United States. Urology. 2019 Dec 30. pii: S0090-4295(19)31126-4.