MRI targeted prostate biopsy: state of the art imaging for the diagnosis of prostate cancer
A 44-year-old healthy man was referred for assessment of high PSA levels by his GP. He had no significant medical/family history and his examination was unremarkable. His PSA was 3.5 ng/ml being 3 ng/ml six months earlier. After discussion with Doctor Zargar, the patient had a multiparametric MRI (mpMRI) of his prostate which demonstrated a 7-mm lesion suspicious for malignancy (PIRADS 4).
The patient underwent transperineal biopsy (systemic grid biopsy) that demonstrated small volume of Gleason 3+3 (ISUP grade I) prostate cancer in the region of mpMRI abnormality. Considering his young age and risk associated with not sampling such a small focus of abnormality seen on mpMRI, he underwent in bore mpMRI guided prostate biopsy.
Four targeted samples from the mpMRI demonstrated abnormality were taken, all four demonstrating Gleason 3+4 (ISUP grade II) prostate cancer. After further counselling about possible options patient elected to undergo robotic bilateral nerve sparing prostatectomy.
The machinery and techniques of prostate MRI have progressed significantly over the past five years. In addition to anatomical assessment of the prostate, inclusion of physiological parameters of the gland such as the behaviour of water in the gland (diffusion weighted imaging) and the interplay between blood vessels and cells in the gland (contrast-enhanced imaging) have increased the accuracy of the MRI and ultimately led to its present-day title: “multiparametric prostate MRI”.
The combination of sequences in a modern mpMRI scan of the prostate is between 80-90% accurate for the diagnosis of prostate cancer. For a small abnormal lesion like the one in our case, the challenge is to ensure that the abnormality is adequately sampled. mpMRI scan not only detects abnormalities but allows targeting of these areas at biopsy rather than the traditional “blind” approach. The abnormal lesions seen on MRI are not always seen during ultrasound guided biopsy. Even with systemic grid sampling of the prostate small lesions can be missed or inadequately sampled.
It is now possible to sample the prostate in several different ways, with mpMRI adding to the accuracy of each method. Having the data from MRI can assist in more precise sampling of the prostate by the urologist (cognitive targeting), or alternatively by fusing the MRI images at the time of biopsy with real-time ultrasound images (fusion targeting) can improve the precision of the biopsy method.
MRI-guided biopsy is another step forward, where the abnormal area in the gland is sampled using the MRI machine itself. This is potentially the most accurate method of biopsy, because it uses one method rather than relying on a fusion of different technologies. Dr Zargar works closely with the MRI radiologist at the Royal Melbourne Hospital offering this state-of-the-art option.