MRI is magnetic resonance imaging using a magnetic field and radio waves.
Currently, the latest 3T MRI studies include diffusion-weighted imaging and dynamic contrast enhancement ie multi-parametric MRI (mp-MRI), to produce detailed images. These studies are undertaken in the supine position without and with intravenous gadolinium contrast.
mp-MRI studied regions of the prostate not detecting disease have about a 95% probability of being free of clinically significant prostate cancer. Since the very common Gleason 3+3=6 disease LACKS the hallmarks of a cancer, it does NOT need detection or treatment. Only clinically significant high-grade prostate cancer requires detection and treatment.
The mp-MRI imaging is superior to standard trans-rectal ultrasound (TRUS) imaging. Compared to mp-MRI, some high-grade cancers can be missed with the random biopsies taken using TRUS imaging.
Before undertaking an mp-MRI study following a biopsy, a waiting period of 6-8 weeks is required to allow healing.
mp-MRI suspicions and PSA-density are significant predictors of prostate cancer.
Prostate cancer is for the most part, a multifocal disease meaning it can exist in several areas of the prostate.
The PSA is not significantly different between men who have multifocal disease compared to unifocal. About 20% of men have a unifocal cancer.
The largest cancer lesion in the prostate is the index lesion and usually it is the dominant area of cancer determining outcome.
The index lesion predicts the clinical outcome in some 90% of men.
The secondary foci of cancer within the prostate usually do not meet criteria for clinical significance (greater than 0.5cc).
Multifocal cancers whether bilateral or not, are not more significant than unifocal.
The presence of secondary foci of cancer appears not to impact recurrence rates.
At present, there is no long-term data to confirm that treating only the index lesion is adequate although there is some information to suggest that this could be so.
NEGATIVE prostate mp-MRI
SUSPICIOUS mp-MRI for prostate cancer and targeted biopsy
- Can be returned to MRI suite at same visit if mp-MRI shows a suspicious area.
- risks of prostate needle biopsy discussed, hematospermia, hematuria, urine infection, urinary obstruction,
- rectal bleeding, fever & chills 1
- no symptoms of acute illnesses
- no anticoagulants
- enema prior to procedure
- IV antibiotics
- oral sedation
- TRUS-guided periprostatic nerve block
- placed in MRI in prone position
- a needle sleeve biopsy guide is placed in the rectum and secured with the localization device to the MRI table
- T2 MRI axial and sagittal images are acquired
- coordinates for biopsying suspicious areas are generated by the software and localizer adjusted
- the 14g hollow needle/trochar is inserted into target lesion and biopsy gun used to take a needle biopsy
- additionally, a random sextant 12-core biopsy is taken till MRI imaging for detecting only the high-grade
- prostate cancers is full-proof
- post-evaluation patient is sent home if in satisfactory condition and voiding, on antibiotics
- all biopsy slides are sent to a recognized prostate cancer reference laboratory for validation of diagnosis