mpMRI vs. TRUS Biopsy: What You Should Know About Your Options
Your doctor says you need a biopsy
If you have had one or more PSA blood tests with an elevated or rising PSA, your doctor may recommend an in-office biopsy guided by ultrasound. This is because only tissue samples can determine whether you have prostate cancer. Right? Actually, no.
You have a choice
A breakthrough type of imaging called Multiparametric MRI (mpMRI) before having a biopsy can reveal cancerous tumors before biopsy because it does what ultrasound cannot do. When performed on a powerful 3T magnet, mpMRI visually reveals the specific characteristics that distinguish tumors from healthy tissue. It does this using two or more special imaging sequences. Each one highlights a particular parameter (function) of prostate tissue. Because it uses more than one parameter, it is multiparametric.
The essential parameters
- T2 weighted images clearly show the prostate zones and suspected tumors that do not look like healthy tissue.
- Diffusion-weighted images (DWI) reveal the movement of water molecules in tissue. Prostate cancer restricts the motion of water molecules, which shows up on DWI-MRI.
- Dynamic contrast enhanced (DCE) MRI reveals the chaotic blood vessels that tumors construct to feed themselves by registering their activity.
Ultrasound imaging can show the size and shape of the prostate gland as well as the needle tracks– but not the exact shape and location of a tumor like mpMRI can. Without knowing where it is, a doctor using ultrasound is aiming blindly.
What mpMRI can do for you
mpMRI gives high resolution 3-dimensional images of the prostate gland showing healthy and unhealthy tissue. If no suspicious tumor is present, a biopsy is not needed and the situation can be monitored by imaging at prescribed intervals if PSA remains high.
It there is a cancer-suspicious area, mpMRI reveals its location, shape and size. Also, experienced readers are able to evaluate the aggression level of such areas based on what the scans show. However, imaging alone is not a diagnosis. This is where a targeted biopsy comes in.
Studies repeatedly confirm that real-time mpMRI guided targeted biopsies, performed in the bore (tunnel) of the magnet, significantly increase the yield and accuracy of diagnosis over TRUS biopsies and avoids unnecessary repeat biopsies. Aiming a minimum number of needles directly into the visible tumor increases the probability of capturing a higher percentage of cancer per needle core as well as the most aggressive cells. This is the most precise biopsy method with the most thorough diagnosis. Plus, the sampled tissue may be submitted for a more detailed genomic cellular analysis.
The information gained from both imaging and biopsy allows the best treatment decision.
Is MRI/ultrasound fusion guidance the same as real time in-bore MRI guidance?
No. It is a “co-registration” of two different imaging technologies: MRI and ultrasound. Previously captured MRI images are “fused” with real-time ultrasound prostate images on a point-by-point input by the doctor; software then generates a synthetic 3-D image of the patient’s gland, reconstructing the location, shape and size of the suspicious area. A needle placement plan is suggested by the software with the doctor able to override it. However, due to different patient positioning between MRI scans and ultrasound—as well as possible patient movement during the ultrasound exam—there will always be a small degree of mismatch and distortion between the static MRI image and live ultrasound.
Urologists who recognize the value of MRI want to bring it into their practice, since fusion-guided targeted biopsy can be done as an in-office procedure. However, it is simply not as precise as a real time in-bore MRI-guided targeted biopsy, which has superior results over all other targeted biopsies.
Advantages of in-bore MRI-guided targeted biopsy at the Sperling Prostate Center
- Images done in real time in the bore of an advanced 3T magnet
- Very high resolution of suspected area allows pinpoint identification
- Minimal needles, minimal trauma to rectal wall and greatly reduced risk of infection or side effects
- If no tumor seen, no need for biopsy at that time but baseline is created for future MRI monitoring
- Verification of location, needle trajectory and placement
- Tissue captured from center of tumor offers most accurate analysis of aggression
- Tissue samples may be submitted for further genomic analysis
- Precise diagnosis fosters best treatment match and customized treatment plans
- Leading U.S. specialist in prostate MRI
MRI-guided targeted biopsy considerations
- Claustrophobic patients may need medication to manage anxiety
- Not widely available in U.S.
- Due to professional learning curve, seek a center with an experienced radiology team
Why shoot in the dark?
Unlike noninvasive MRI, prostate ultrasound imaging is done by inserting a lubricated ultrasound wand into the rectum. This type of biopsy is called Transrectal Ultrasound (TRUS) guided biopsy. Because ultrasound can’t reveal the tumor, the doctor can’t “see” what he’s looking for. Aiming needles into the prostate gland using ultrasound is like shooting in the dark. It generally involves taking 12-14 needle samples according to a systematic template consisting of half of the samples taken from each side of the gland. While TRUS biopsy is economical due to the in-office equipment, it has downsides and risks.
- False-negative rates of up to 30% (biopsy needles missed the tumor) – leads to a false sense of relief
- Under-grading the aggression level of the tumor because the samples did not include the most dangerous cells)
- Overdetection of prostate cancer that is not significant (also called indolent prostate cancer)
- The need for repeat biopsies when PSA continues to rise despite negative biopsies.
Reported risks and side effects
- Discomfort, even pain that increases with the large number of samples taken
- Risk of infection that increases with the number of needles used
- Risk of side effects, including urinary and sexual problems
- Blood in urine (hematuria)
- Blood in semen (hemospermia)
- Post-biopsy hospitalization due to complications
- Repeat biopsies after false negative biopsies
- Continued cancer growth and progression if the biopsy misses cancer