Current prostate cancer diagnostic techniques are being scrutinized due to lack of conclusive data from screening trials and concerns about large number of unnecessary biopsies that are being performed.Nearly a million biopsies are done annually, to detect only a quarter of a million prostate cancer cases, which means 75% biopsies are unnecessary. PSA is an imperfect biomarker, missing 15% cases of prostate cancer when PSA is normal and when PSA is abnormal only 12% cases are found to have cancer. This leads to unnecessary blind and random biopsies, of which a large number turn out to be negative or of indolent cancers and is also associated with underestimating the cancer stage and missing significant Gleason 7 cancer in up to 30% cases. PSA as a marker and systematic biopsy as a confirmation tool are far from perfect and there is an acute need for developing better biomarkers and increasing accuracy of our biopsy techniques. Thus, the current diagnostic tools are imperfect to distinguish between aggressive prostate cancers requiring treatment, from indolent cancers.
The MRI-TRUS fusion is done in two steps: first a multiparametric endorectal MRI is done, the studies are then loaded on to a software on which the radiologist marks the prostate gland and the regions of interest for biopsy in different slices and views of the MRI, known as segmentation. This information is then loaded on to the device. The second step involves real-time MRI-TRUS fusion to create a three-dimensional real-time reconstruction of the prostate on which the aiming and tracking of biopsy site is done. This technique can be done in an outpatient setting under local anesthesia within a few minutes. Currently five devices approved by the FDA are available for MRI-TRUS fusion biopsy. The Artemis device (Eigen, GrassValley, California, USA) has a mechanical arm with ultrasound transducer probe and is capable of tracking and recording biopsy locations.
The initial study at UCLA in 171 patients who underwent prostate biopsies using the Artemis platform which included 106 (active surveillance) patients and 65 (increasing PSA, prior negative conventional biopsy)patients. Prostate cancer was detected in 53% of the men. Fusion biopsy based targeted cores had higher yield of 21% as compared to 7% for systemic biopsy cores and higher number of gleason 7 cores 36% vs 24%.
Multi-parametric MRI is capable of showing the location, extent and aggressiveness of prostate cancer. This capability of MRI is expected to end the era of unnecessary blind prostate biopsies and pave the way for future image-guided biopsies. It will help tailor therapies based on each patient's unique individual requirements and lead to improvements in health care and reduce complications, patient anxiety and discomfort.