Munich, Germany (UroToday.com) In today’s plenary session 2 at the 2016 EAU meeting, Dr. Eduard Baco posed and then comprehensively answered the debate question as to whether there is a role for pre-biopsy MRI. He began by reporting that there are approximately 1 million prostate biopsies done annually in Europe, including those done in the primary setting, patients with previous negative biopsies, active surveillance cohorts, and post treatment patients. The question with the emergence of MRI is whether this number can be filtered down, and this depends on availability and cost effectiveness of MRI, as well as a universally accepted structured reporting methodology.
The utility of mpMRI in the setting of clinically significant CaP hinges on the establishment of an acceptable negative predictive value. Review of literature shows that this rate varies from 63% to 98%; this highlights the differences in definitions of “significant” cancer used across the series (Epstein, START, UCL 1 and 2, MR-TRUS fusion bx). In general, a higher threshold definition results in improved NPV.
In the pre-biopsy setting, MRI can be useful for detection of an index lesion, it can rule out clinically significant cancer, and replace screening biopsies with fewer targeted cores via MRI/TRUS fusion. In the primary setting, 2 RCTs showed no benefit of MR/TRUS + standard 12-core biopsy vs. standard 12-core biopsy alone in terms of detection of clinically significant CaP. However, 2 cores in an MR/TRUS fusion biopsy was comparable to 12-core standard biopsy, so while there was no benefit in terms of cancer detection rate, fewer cores were necessary to achieve the same result. Results were more encouraging in a selected population of men undergoing repeat biopsy following a negative biopsy: overall there was a 42% cancer detection rate, including 81% on anterior MRI lesions. Overall cancer detection rate improved to 81-96% when only considering PIRADS 4 and 5 lesions, and 68-86% for clinically significant disease.
Among active surveillance patients, it is known that we have historically under-sampled significant tumors at initial biopsy. Confirmatory MR/TRUS fusion biopsy can reclassify up to 1/3 of patients who initially met criteria for AS. Dr. Baco emphasized that selection of patients for AS should be based on combination of systematic and MRI-TRUS targeted prostate biopsy. In the post-radiation setting, MRI can detect and localize recurrence of disease. Morgan et al demonstrated 79% cancer detection rate on MR/TRUS biopsy among men with BCR. Finally, MRI can detect the index tumor in up to 94% of patients, with MR/TRUS biopsy accurately characterizing these lesions in 95% of cases.
Aside from the detection of significant CaP and characterization of index lesions, MRI can be useful in ruling out significant cancer in the pre-biopsy setting. However, 10-20% of clinically significant cancers are MRI invisible; thus, Dr. Baco recommends that all men with a negative MRI and suspicion for CaP should still undergo standard 12-core biopsy. In select patients, adjunct tests such as PHI, PCA3, 4k score, reviewed or repeated MRI, or molecular imaging may assist in decision-making as well. Given the rate of missed cancers on MRI, along with the 5-20% rate of missed cancers on targeted biopsy, a targeted-only strategy is not ready for prime time.
Dr. Baco concluded that the greatest benefit of pre-biopsy MRI is found in patients undergoing re-biopsy. The main role is to detect clinically significant cancer and localize the index lesion. NPV is highly dependent on methodology and selection criteria. Systematic biopsy should be performed in addition to targeted approach in the initial biopsy session. Finally, close cooperation between urologist and radiologist is mandatory for successful outcomes.
Presented By:
E. Baco, Oslo (NO)
Reported By:
Nikhil Waingankar, MD, at the 31st Annual EAU Congress - March 12 - 15, 2016 – Munich, Germany
Fox Chase Cancer Center