By: Dan Sperling, MD
I was a bit shocked when I came across an older research study titled “Two Consecutive Sets of Transrectal Ultrasound [TRUS] Guided Sextant Biopsies of the Prostate for the Detection of Prostate Cancer.”[i] I could hardly believe my eyes—two consecutive TRUS biopsies? The study is from 1998, and it gave me perspective on how far we’ve come since then. While the idea of undergoing two TRUS biopsies in a single visit may sound awful, it’s important to understand that “sextant” biopsies only take six needles, and they were still the norm in ‘98. Researchers were starting to wonder if such a small sampling grid was undersampling, even missing, significant cancer. Thus, the purpose of this study was to explore whether adding a second biopsy during the same appointment would increase the chances of detecting cancer.
In fact, this proved to be the case. A total of 137 patients who had either a positive digital rectal exam and/or an elevated PSA each had two consecutive sets of TRUS sextant biopsies in a single visit. 43 of them (31%) were diagnosed with prostate cancer. In 13 of the patients (10%) it was discovered only from the second biopsy. According to the article, “The second set of biopsies provided important new clinical information related to prostate cancer in 20 cases (28%) and increased the number of cancers detected by 30%…The benefits include increasing the detection of adenocarcinoma of the prostate and providing the recommended second set of biopsies for high grade intraepithelial neoplasia[ii] without increased morbidity or cost.”
In the years following, the number of TRUS biopsy needles increased from six to today’s 10-12 needles. In other words, more needles were added in an effort to sample the gland more widely, and thus avoid missing cancer. So instead of two 6-needle biopsies, the standard became twice as many needles in a biopsy. All of this had to occur because ultrasound cannot discriminate tissue differences, so TRUS biopsies have a hit-or-miss quality.
We’re progressed a very long way from 1998, thanks to 3T multiparametric MRI. We now have visual guidance that can reveal suspicious areas in very good detail. This is so superior to ultrasound that it allows us to direct a minimum number of biopsy needles directly into the core of such regions. There is a very high likelihood that we are not only finding the cancer, but also that our evaluation of how aggressive it is (Gleason grade) is accurate.
We can close the book on the old-fashioned TRUS-guided sextant biopsy. We can be grateful that we can offer patients a valuable alternative that minimizes time and discomfort while maximizing the important information that only a biopsy can give.
[i] Levine MA, Ittman M, Melamed J, Lepor H. Two consecutive sets of transrectal ultrasound guided sextant biopsies of the prostate for the detection of prostate cancer. J Urol. 1998 Feb;159(2):471-5.
[ii] High grade intraepithelial neoplasia refers to abnormal cells that are likely to become cancerous.