ASCO GU 2018: Case-Based Debate: Magnetic Resonance and Magnetic Resonance-Directed Biopsy: Where is the Field Moving?

San Francisco, CA (UroToday.com) In this opening session of the Genitourinary Cancers Symposium 2018, Drs. Emberton and Pedrosa shared their data and experiences with MR and MR directed biopsy in evaluation of prostate cancers. Three patient scenarios were then discussed with the panel. The current AUA and SAR standard strongly considers MRI for a patient with continuing concern for prostate cancer and a previous negative biopsy. However, the method of MR directed biopsy is under debate. Cognitive fusion, MRI gantry “in line” and MRI fusion biopsies are all accepted evaluation methods. The value of additional systemic biopsies is not clear at this time. While this adds sensitivity, it may lead to more insignificant prostate cancers (over-detection). NCCN 2017 guidelines suggest that physicians can consider multiparametric MRI in patients with elevated PSA who have not had prior TRUS guided biopsy.

The first patient scenario was a 50 year-old Caucasian male with an initial PSA of 3.0 ng/ml (repeat 3.1 ng/ml) and a normal DRE but a positive family history. The initial question was how the audience (and panel) would evaluate this patient. Most of the audience wanted to proceed with MRI, a large percentage also wanted a free and total PSA. Seven published randomized trials have compared MRI to current standard of care. Three of these trials have positive results, two of which had a primary outcome of clinically significant cancer (as opposed to ANY cancer). Data from the PROMIS trial, published in Lancet in 2017, demonstrated a 48% sensitivity of TRUS biopsy for detecting clinically significant cancer as opposed to 93% sensitivity for MRI.

Additionally, there is debate regarding the necessity of repeat systematic prostate biopsy for active surveillance patients in the face of a normal MRI. Given the false negativity rates are extremely low, this may not be necessary.

The next portion of the debate was to focus on the optimal type of MRI performed. Here, Dr. Pedrosa demonstrated there is no difference in diagnostic accuracy for index lesions for 3T MRI with a surface coil alone versus a surface coil and endorectal coil. Clearly, patients prefer MRI without endorectal coil, if possible. The performance of 1.5T MRI without endorectal coil is still extremely good with a sensitivity of 88%, specificity of 43%, positive predictive value 65%, and negative predictive value of 76% for clinically significant cancers. This data should be used for future comparison. The PI-RADS version 2 panel has stated that both 1.5 and 3.0 T can provide adequate and reliable diagnostic exams when acquisition parameters are optimized and appropriate and contemporary technology is employed. Most members of the PI-RADS steering committee prefer 3T for prostate MRI if possible. Endorectal coil is valuable for high special resolution imaging (staging) and lower SNR sequences (DWI, DCE) and larger patients. Increasing cost and time of MRI, deforms the gland, and introduces artifacts. This may be uncomfortable for patients and increase their reluctance to undergoing MRI.

Dr. Pedrosa states that there is no standardization for image and examination quality, which often varies across treatment centers, and there is no formal mechanism for radiologists to become certified in prostate MRI. It is critical that interpreting radiologists participate in ongoing case review in the future and we develop systems based improvements.

Presented by: Mark Emberton, MD, University College Hospital and Ivan Pedrosa, MD, UT Southwestern Medical Center

Written by: David B. Cahn, DO, MBS, Twitter: @dbcahn, Fox Chase Cancer Center-Temple Health, Philadelphia, PA at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA
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