Presentation Authors: Michael Liss*, San Antonio, TX, Michael Garcia, Yingye Zheng, Lisa Newcomb, Seattle, WA, Christopher Filson, Atlanta, GA, Hilary Boyer, Seattle, WA, James Brooks, Stanford, CA, Peter Carroll, San Francisco, CA, Martin Gleave, Vancouver, Canada, Francis Martin, Virginia Beach, VA, Todd Morgan, Ann Arbor, MI, Peter Nelson, Seattle, WA, Andrew Wagner, Boston, MD, Ian Thompson, San Antonio, TX, Daniel Lin, Seattle, WA
Introduction: MRI has been shown to increase detection of clinically significant cancer in the initial diagnosis of prostate cancer. We aim to investigate the ability of multiparametric MRI to detect Gleason Grade Group (GG) â‰¥2 cancer in a multi-institutional active surveillance cohort with standardized follow up and biopsy protocols.
Methods: Men enrolled in PASS across ten institutions were examined to identify men who underwent a biopsy within 12 months of a multiparametric MRI. Local interpretation of MRI PIRADS scores and biopsy GG were used in the analysis. MRI with no lesions or PIRADS 1-3 were considered negative and MRI with PIRADS 4-5 was considered positive. We investigate the performance MRI to detect GG2 or greater disease, controlling for the clinical factors of age, BMI, the proportion of positive cores, prostate size and PSA. We also compared GG found in systematic vs targeted cores in fusion biopsies.
Results: We evaluated 351 MRIs from 325 individuals. The negative predictive value (NPV) of MRI for any GG2 or greater was 76% with a false positive rate of 49%. A negative MRI was significant in a multivariable logistic regression (OR 0.55, CI 0.32-0.93; P=0.03). In a sensitivity analysis of 287 MRI in 270 men with only GG1 cancer prior to MRI, biopsy reclassification to GG2 was observed in 27/127 (21%) of negative MRI and 49/139 (35%) of positive MRI. In this subset, negative MRI was not associated with reclassification to GG â‰¥2 in the multivariable model. In 192 fusion biopsies, GG concordance between the target and systematic biopsies was 81% (156/192). Targeted biopsies identified higher GG than systematic biopsy in 8% (15/192) of men; whereas, systematic biopsy identified higher GG than targeted in 11% (21/192).
Conclusions: While MRI is often used in active surveillance, the NPV of MRI is only 76% and false positive rates may limit the widescale applicability. Systematic biopsy still detects higher GG lesions in 11% suggesting that systematic biopsy cannot be omitted in the setting of positive or negative MRI.
Source of Funding: Canary FoundationDoD grant #W81XWH1410595DoD grant #W81XWH1510441