ESOU18: MRI in-bore Guided Biopsies
The possible in-bore biopsy approaches include trans-perineal, trans-gluteal and transrectal. The advantages of the transrectal approach include the fact that it does not require anesthetics, it is usually well tolerated, and it is easier to perform. However, it does harbor a significant risk of infections with 1-2% risk of urosepsis.
The accepted indications for MRI guided biopsies today include elevated PSA, suspicious lesion on MRI, a previous negative TRUS biopsy and perhaps biochemical recurrence after radiotherapy. Patient preparation includes antibiotics, sexual abstinence for 4 days prior biopsy to distend the seminal vesicles, and holding off all anticoagulation treatments. The patient is positioned in the scanner table with head first prone. The biopsy workflow consists of identification of the cancer suspicion area, targeting of that area, obtaining of biopsy sample and performing a confirmation scan.
Studies have shown that 42% of patients with a PIRADS 3 lesion with PSA density above 0.15 could avoid a biopsy, while 6% of clinical significant cancers would be missed if a biopsy was not performed. The median PC detection rate is 42% in patients with elevated PSA and a prior negative TRUS biopsy. Most cancer detected are significant (81-93%). In patients with suspicion of biochemical recurrence after radiotherapy, the positive predictive value is 86% compared to 27% in TRUS biopsies.
Contraindications for in-bore biopsies include the common MRI contraindications – pacemaker, non-compatible metallic implants and severe claustrophobia. The challenges that are needed to overcome are the fact that this is a time-consuming procedure (45-60 min per patient), the need for repeated needle guide adjustments, target displacement and patient movement. However, there are technological improvements under work to attempt to reduce the procedure time.
In summary, in-bore MRI guided biopsy is a very accurate diagnostic tool. However, due to limited availability, and costs, it should be reserved for selected patients (small lesions <5 or 10 mm, anterior lesions, discrepancy between mpMRI and pathology, and biochemical recurrence cases).
Speaker: J.P. Michiel Sedelaar, MD Professor, Department of Urology Radboud University Medical Centre in Nijmegen, Netherlands.
Written By: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre @GoldbergHanan at The 15th Meeting of the EAU Section of Oncological Urology ESOU18 - January 26-28, 2018 - Amsterdam, The Netherlands