AUA 2018: Negative MRI: Which Patients Could Safely Avoid Prostate Biopsy?

San Francisco, CA USA (UroToday.com) Over the last year, two impactful trials have propelled mpMRI into the spotlight for detection of prostate cancer [1,2]. The PROMIS trial subjected 576 men with a clinical suspicion of prostate cancer and no previous biopsy to mpMRI + TRUS biopsy, as well as a reference test (a template prostate mapping biopsy) [1]. Clinically significant prostate cancer was Gleason ≥4+3 or a maximum cancer core length of ≥6 mm. On reference biopsy, 71% of men had cancer, with 40% of the 576 patients having clinically significant prostate cancer. Among patients with clinically significant cancer, mpMRI was more sensitive (93%, 95%CI 88-96%) than TRUS biopsy (48%, 95%CI 42-55%, p<0.0001). However, mpMRI was less specific (41%, 95%CI 36-46%) than TRUS biopsy (96%, 94-98%, p<0.0001). The PRECISION trial randomized 500 biopsy naïve men to mpMRI with (if the MRI was suggestive of cancer) or without targeted biopsy or standard TRUS biopsy [2]. Men whose MRI was not suggestive of cancer were not offered a biopsy. In the MRI group, 28% had non-suspicious MRIs and thus did not undergo biopsy. Clinically significant cancer was detected in 38% of men in the MRI-targeted biopsy group, compared to 26% in the TRUS biopsy group (p=0.005).

Furthermore, fewer men in the MRI-targeted biopsy group than the TRUS biopsy group received a diagnosis of clinically insignificant cancer (-13 percentage points). As such, Dr. Oishi from USC presented their experience with assessing the diagnostic accuracy of mpMRI to rule out clinically significant and high-grade prostate cancer
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For this study, the authors identified 401 patients from their prostate biopsy database from October 2011 to March 2017 at two US referral centers. These patients met inclusion criteria if they had a negative mpMRI prior to prostate biopsy, which was defined as Prostate Imaging-Reporting and Data System (PIRADS) score <3 or Likert score <3. Clinically significant prostate cancer was defined as Gleason score ≥ 3+4, and high-risk prostate cancer was defined as GS ≥ 4+3. Exclusion criteria was patients with prior treatment for prostate cancer. Radiologists were divided into two groups: experienced radiologists (n=4) that reported more than 40 MRIs and other radiologists that reported less than 40 MRIs in this cohort.

The median age of patients in this study was 63 years (IQR 58-68), median PSA was (6.4 ng/mL (IQR 4.6-8.6), median prostate volume was 52 cc (IQR 36-72), and median PSA density (PSAD) was 0.12 ng/mL/cc (IQR 0.078-0.18). Fifty-two (13%) patients were African American. Of 401 patients, 107 (27%) were prostate biopsy-naive, 212 (53%) had previous negative prostate biopsy, and 79 (20%) had a previous positive biopsy. The median number of core biopsies per patient was 14 (IQR 12-15). Overall, there were 136 patients (33.9%) diagnosed with prostate cancer of which 46 patients (33.8%) had clinically significant disease and 20 (14.7%) patients had high-risk disease. The negative predictive values (NPV) for detecting any prostate cancer was 66%, for clinically significant prostate cancer was 89%, and for high-grade prostate cancer was 95%. On multivariable analyses, PSAD < 0.15ng/mL/cc and history of previous negative prostate biopsy (OR 0.326, 95%CI 0.169-0.628, p<0.001 and OR 0.393, 95%CI 0.200-0.774, p=0.0069, respectively) were independent predictors for non-clinically significant prostate cancer. PSAD < 0.15ng/mL/cc and experienced radiologists were independent predictors for non-high risk prostate cancer (OR 0.265, 95%CI 0.097-0.720 p=0.0095 and OR 0.29, 95%CI 0.103-0.817 p=0.019, respectively).

The strength of this study is the pragmatic approach including patients without prior prostate biopsy, those with prior negative biopsy, and men with previous positive biopsy. This study adds to the growing body of literature supporting mpMRI in the detection of clinically significant prostate cancer. A limitation of the study is the lack of a comparator arm for patients undergoing mpMRI. Dr. Oishi concluded that patients with PSAD < 0.15ng/mL/cc and a history of previous negative biopsy may avoid repeat prostate biopsy if MRI is negative. Furthermore, PSA, age and race were not predictors for clinically significant prostate cancer in the setting of negative MRI.

Presented by: Masakatsu Oishi, USC Institute of Urology, Los Angeles, CA

Co-Authors: Thomas B. Smyth, Owings Mills, MD, Toshitaka Shin, Chisato Ohe, Luis Medina, Akbar Ashrafi, Giovanni Cacciamani, Sunzanne Palmer, Manju Aron, Los Angeles, CA, Ronald F Tutrone, Owings Mills, MD, Osamu Ukimura, Kyoto, Japan, Inderbir S. Gill, Andre Luis de Castro Abreu, Los Angeles, CA

Written by: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre, Twitter: @zklaassen_md, at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA

References:
1. Ahmed HU, El-Shater Bosaily A, Brown LC, et al. Diagnostic accuracy of multi-parametric MRI and TRUS biopsy in prostate cancer (PROMIS): A paired validating confirmatory study. Lancet 2017;389(10071):815-822.
2. Kasivisvanathan V, Rannikko AS, Borghi M, et al. MRI-targeted or standard biopsy for prostate cancer diagnosis. N Engl J Med 2018;378(19):1767-1777.
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