BackgroundTo investigate tumor aggressiveness in peripheral zone prostate cancer (PCa) by correlating Gleason score (GS) with diffusion tensor imaging (DTI) from multiparametric magnetic resonance imaging (MRI) at 3.0 Tesla (T). MethodsEighty-three patients with pathological proven peripheral zone PCa whose GS in at least one core biopsy met the criteria(GS 3+3, GS 3+4, GS 4+3, or GS 4+4) were included in this study. DTI was performed using b values of 0 and 800 s/mm(2) with 32 directions in all patients on a 3.0T MRI scanner. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were calculated from the DTI data of patients with the previously mentioned four categories of Gleason scores. An association between DTI measurements(FA, ADC) and GS was tested using the Spearman rank correlation analysis. ResultsFA values in the sextants found to harbor cancer were positively correlated with the GS(r=0.48; P<0.001), while the ADC values were negatively correlated with GS(r=-0.54; P<0.001). Statistical significance(P<0.05) was found for FA values among different GS groups, with the exception of GS 3+4 versus GS 4+3 (P=0.105). The differences between the ADC values were statistically significant for all four different scores(all P<0.05). ConclusionQuantitative DTI at 3.0T MRI shows a significant association with GS in the evaluation of tumor aggressiveness in peripheral zone PCa, which may be useful to ensure concordance of biopsy results and therefore make the appropriate decision in the management of patients with PCa. J. Magn. Reson. Imaging 2015;42:460-467.