MP42-04 MAPPING OF TRUE POSITIVE, FALSE POSITIVE AND FALSE NEGATIVE LYMPH NODES AFTER SALVAGE LYMPH NODE DISSECTION IN PROSTATE CANCER PATIENTS WITH POSITIVE NODES AT 11C CHOLINE POSITRON EMISSION TOMOGRAPHY/COMPUTED TOMOGRAPHY

Abstract

INTRODUCTION AND OBJECTIVES: Prostate cancer and chronic prostatitis can both lead to elevated prostate specific antigen (PSA). Conventional magnetic resonance imaging (MRI) imaging features distinguishing prostate cancer from chronic prostatitis are not well established and therefore differentiation of those two entities is important to avoid over and underestimation of the extent of prostate cancer. The purpose of this study was to describe characteristics of chronic prostatitis using high spatial resolution dynamic contrastenhanced MRI (HR-CE-MRI) with correlative histopathology from prostatectomy specimens. METHODS: Following IRB approval, 54 consecutive patients with prostate cancer scheduled for prostatectomy underwent pre surgical endorectal coil MRI on a 1.5 Tesla scanner between January 2012-July 2013, obtaining high-spatial resolution T2-weighted and dynamic CEMRIs of the prostate. MRI features suggestive of chronic prostatitis were compared to prostatectomy specimens. Descriptive statistics including accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (PPV) were calculated. Agreement between presence of chronic prostatitis at HR-CE-MRI and at final diagnosis was evaluated using kappa (k) statistics. RESULTS: Imaging features most suggestive of chronic prostatitis include late-enhancing pseudoseptations with fine, linear striations in a centrifugal pattern irrespective of rapid wash-in within areas with preserved pseudoseptations on dynamic HR-CE-MRI. In contrast, cancerous areas showing rapid wash-in and wash-out, never showed late enhancing fine linear striations. Of 54 patients, 46 had chronic prostatitis by histopathologic criteria; 49 had MRI findings suggestive of chronic prostatitis with 3 false positives. These findings had a sensitivity of 100%, specificity of 62.5%, PPV of 93.8%, and NPV of 100%. The accuracy (observed agreement) was 94.4%. There was substantial agreement between presence of chronic prostatitis at CE-MRI and at final diagnosis (kappa1⁄4 0.74, standard error1⁄4 0.141). CONCLUSIONS: Key imaging features distinguishing chronic prostatitis and prostate cancer were found to have a sensitivity of 100%. These preliminary results demonstrate an accurate method for distinguishing these two entities and can lead to more accurate MRI staging of prostate cancerwhichcanaffect treatment choiceandclinical outcome.