Prospective evaluation of endorectal magnetic resonance imaging to detect tumor foci in men with prior negative prostatic biopsy: A pilot study

Purpose: Prostate cancer foci have a characteristic appearance on endorecta l magnetic resonance imaging (MRI) which might be useful for prostate cance r detection. In this pilot study the ability of endorectal MRI to detect pr ostate Cancer foci prospectively in men at risk for a malignant prostatic n eoplasm is assessed. Materials and Methods: Endorectal MRI was performed in 33 consecutive men w ith 1 or more prior negative prostatic biopsies; All studies were read by 2 MRI dedicated study radiologists in consensus before and after receiving p atient clinical data. Areas of interest on endorectal MRI were mapped as lo w, moderate or high suspicion for carcinoma on a prostate model. Directed n eedle biopsy cores of the prostate were obtained based on this model, and t he histopathological findings were compared with MRI results. Results: Carcinoma was detected in 7 of 33 men (21.2%) on post-MRI biopsy, including 1 of 18 (5.6%) with low, 1 of 8 (12.5%) with moderate and 5 of 7 (71.4%) with high suspicion MRI. The site of positive biopsy correlated cor rectly with the area of suspicion on MRI in 85.7% of cases. Overall, endore ctal MRI had 40% positive predictive value (moderate or high suspicion), 94 .4% negative predictive value (low suspicion) and 69.7% accuracy. On multiv ariate analysis positive endorectal MRI was associated with an 11.3-fold ri sk of positive biopsy. Conclusions: Endorectal MRI may effectively stratify patients with prior ne gative prostatic biopsy into low, moderate and high risk groups for a malig nant prostatic neoplasm, and may improve our ability to identify prostatic tumor foci prospectively.