By: Dan Sperling, MD
Currently, the 12-core transrectal ultrasound guided biopsy (TRUS-GB) is considered the “gold standard” for diagnosing prostate cancer (PCa). However, such biopsies miss PCa roughly 30% of the time, which is called a false negative. Such a high rate of false negatives has been shown in studies such as that by Serefoglu et a. (2013) which did a case-by-case comparison of presurgical biopsy results with the actual cancer found in the same post-prostatectomy specimens.[i] What’s worse, “… repeat biopsies can still be negative despite the patient’s reality of having prostate cancer,” according to Serefoglu paper. This suggests that subsequent 12-core biopsies are following the same sampling template repeatedly, only to miss the same cancers that eluded detection in the first place. Certain factors tend to increase the detection rate of TRUS biopsy, including more needles, smaller prostate glands, higher PSA and younger patient age, but the fact remains that TRUS biopsy has inherent flaws that it has not been able to overcome, especially for patients who have had at least one negative biopsy but whose PSA remains suspiciously high.
A solid study out of Germany did a head-to-head comparison of real-time MRI-guided (in-bore) targeted prostate biopsy vs. standard TRUS biopsy (Kaufmann et al., 2015).[ii] Thirty-five patients who previously had at least one negative TRUS biopsy were enrolled. Each of them had a 3T multiparametric MRI scan; experienced readers scored suspicious lesions using the PI-RADS scale (for more information on PI-RADS, see https://sperlingprostatecenter.com/pi-rads-score/ and https://sperlingprostatecenter.com/testing-pi-rads-accuracy/.) An average of three targeted biopsy needles per lesion were obtained while under MRI guidance. Following these biopsies, each patient had a 12-core TRUS biopsy done by a urologist who was unaware of the MRI findings. The two types of biopsy results were then compared for each patient, with attention to the location of positive findings and whether the tumors were clinically significant based on Gleason score. The authors report detection rates were twice as high for MRI-guided in-bore targeted biopsy:
|Biopsy Type||Detection rate|
|MRI guided in-bore targeted biopsy||46% (16 of 35 patients)|
|TRUS guided standard biopsy||23% (8 of 35 patients)|
According to their results, the in-bore biopsies detected prostate cancer in all the patients whose TRUS biopsy found it, as well as 8 additional patients whose TRUS biopsy produced false negatives (missed the cancer.) Definitions of “clinical significance” vary but usually include Gleason score > 3+3 and tumor volume > 0.5 cm3, and the research team found that all tumors detected by in-bore targeted biopsy “exhibited at least one criterion of clinical significance. They concluded that in-bore biopsy is “more effective compared with TRUS-GB in detecting clinically significant PC in men after previous negative TRUS-GB.” PI-RADS scores give additional information and could be part of the decision-making process when considering retrial biopsy. Additional systematic biopsy can be omitted in patients undergoing targeted MR-GB.
Interested readers can find additional data on in-bore biopsy at the following links:
As the body of published literature on real-time MRI-guided in-bore biopsy grows, we can expect future research to bear out the superiority of this method, which is not only more accurate but is also easier for patients since fewer needles are involved. One final feature worth noting: experts have calculated that there are economic benefits as well, since accuracy with the first biopsy saves long-term medical costs involved with repeat TRUS biopsies, side effects of repeat biopsies, and diagnosing missed PCa at later stages when treatment is more costly.
[i] Serefoglu EC, Altinova S, Ugras N, Akincioglu E et al. How reliable is 12-core prostate biopsy procedure in the detection of prostate cancer? Can Urol Assoc J. 2013 May-Jun; 7(5-6): E293–E298.
[ii] Kaufmann S, Kruck S, Kramer U, Gatidis S et al. Direct comparison of targeted MRI-guided biopsy with systematic transrectal ultrasound-guided biopsy in patients with previous negative prostate biopsies. Urol Int. 2015;94(3):319-25.