Precision detection and diagnosis of clinically significant PCa (csPCa) is essential to identify which patients require immediate treatment. Adding multiparametric MRI (mpMRI) into the diagnostic pathway has revolutionized the detection and diagnosis of clinically significant prostate cancer (csPCa). “Significant” means PCa that should be biopsied to determine accurate diagnosis. mpMRI together with standardized PI-RADS scores, offers high detection rates of csPCa. Nowadays, use of mpMRI prior to biopsy is increasing dramatically in order to rule out unnecessary biopsy.^[i]

If biopsy is indicated based on mpMRI, biopsy needles can be selectively targeted into suspicious lesions. This overcomes the shortcomings of randomized TRUS-guided systematic biopsies.^[ii]

Three targeting methods

Studies demonstrate that mpMRI-guided targeted biopsies increase the yield and accuracy of diagnosis over standard TRUS biopsies, by capturing a higher percentage of cancer per needle core as well as the most aggressive cells. Typically, a real-time (in-bore) mpMRI guided biopsy requires 2-4 needles, reducing risks associated with TRUS-guided 12-14+ needle biopsy. There are three methods for targeting needles based on mpMRI images:

1. Cognitive fusion – This is a 2-step process. First, the patient has an MRI, with images and written report transmitted to his urologist. Then, based on MRI results, the doctor mentally calculates where to place TRUS-guided biopsy needles. Though TRUS cannot depict tissue differences, it confirms needle placement as the doctor mentally calculates a pathway into the target.
2. MRI/ultrasound fusion (MR/US fusion or co-registration) – This is also a two-step process. Previously captured MRI images are “fused” with real-time ultrasound images of the gland; software generates a 3-D image of the patient’s gland, constructing the location, shape and size of the suspicious area. However, the prostate seen by the doctor on real-time ultrasound will never exactly match the MRI scan. This is called registration error. It occurs because imaging angles and patient movement can confound accuracy, so additional needle sampling is recommended to compensate.
3. In-bore MRI guidance – In a single step, mpMRI identifies suspicious lesion(s) and guides needle pathways in real time for optimum accuracy. The low number of needles reduces risks associated with TRUS biopsy.

Is one of these methods better? Acar et al (2015) designed a study comparing the diagnostic accuracy of standard TRUS systematic biopsy vs. cognitive fusion targeted biopsy, and real-time in-bore mpMRI targeted biopsy in patients with positive screening indications for cancer but no previous biopsy.^[iii] They retrospectively analyzed the clinical charts of 140 patients, all of whom had mpMRI prior to any biopsy. The imaging sequences included T2-weighted MRI, diffusion weighted MRI, and dynamic contrast-enhanced imaging. According to the authors, “Cognitive fusion biopsies were performed after a review of mp-MRI data, whereas TRUS-guided biopsies were performed blinded to MRI information. In-bore biopsies were conducted by means of real-time targeting under MRI guidance.” All men were treated by radical prostatectomy, and the pathology reports on the gland specimens were available for comparison with biopsy results. Diagnosis rates of prostate cancer (PCa) were as follows:

Biopsy type	TRUS (37 men)	Cognitive fusion (49 men)	In-bore (14 men)
PCa diagnosis rate	51.3% PCa	55.1% PCa	71.4% PCa
Biopsy detection of csPCa	69.1%	70.3%	90%
Prostatectomy detection csPCa	85.7%	93.3%	100%

A more recent comparison of in-bore vs. fusion biopsy (cognitive-guided biopsy was not included) reported that in-bore biopsy had “significantly greater likelihood of detection of any cancer” vs. fusion targeting. However, when fusion-guided biopsy was supplemented with systematic biopsy, there was no significant difference in cancer detection. Given the minimal number of needles used for in-bore biopsy without additional systematic sampling (reducing biopsy risks while enhancing accurate diagnosis), the authors conclude, “… in-bore MRI-targeted prostate biopsy had a higher target-specific cancer detection rate than did fusion biopsy. … Pending a larger prospective randomized multicenter comparison between in-bore and fusion biopsy, in-bore may be the preferred approach should performing only biopsy of a suspicious target, without concurrent systematic biopsy, be considered clinically appropriate.”^[iv]

Additional factors may influence choice of biopsy guidance. Primary, of course, are the patient’s clinical indications as well as availability of device(s). In many healthcare systems, economy may also be a determinant. In any case, research evidence suggests the desirability of in-bore MRI targeted biopsy due to its diagnostic edge over fusion and cognitive guidance.

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

References

[i] Launer BM, Ellis TA, Scarpato KR. A contemporary review: mpMRI in prostate cancer screening and diagnosis. Urol Oncol. 2024 Aug 10:S1078-1439(24)00485-X. doi: 10.1016/j.urolonc.2024.05.012.
[ii] O’Connor LP, Lebastchi AH, Horuz R et al. Role of multiparametric prostate MRI in the management of prostate cancer. World J Urol. 2021 Mar;39(3):651-659. doi: 10.1007/s00345-020-03310-z.
[iii] Acar Ö, Esen T, Çolakoğlu B, Vural M et al. Multiparametric MRI guidance in first-time prostate biopsies: what is the real benefit? Diagn Interv Radiol. 2015 Jul-Aug;21(4):271-6. doi: 10.5152/dir.2015.46014.
[iv] Prince M, Foster BR, Kaempf A et al. In-Bore Versus Fusion MRI-Targeted Biopsy of PI-RADS Category 4 and 5 Lesions: A Retrospective Comparative Analysis Using Propensity Score Weighting. AJR Am J Roentgenol. 2021 Nov;217(5):1123-1130. doi: 10.2214/AJR.20.25207.