Multiparametric MRI identifies and stratifies prostate cancer lesions: implications for targeting intraprostatic targets.

PURPOSE To assess the ability of multiparametric (mp) MRI (mp-MRI) to identify, stratify, and localize biopsy-proven prostate cancer lesions in a risk-stratified patient population. METHODS AND MATERIALS We retrospectively analyzed 57 patients who had mp-MRI and core needle biopsy during diagnostic prostate cancer evaluation. The MRI sequences were scored for suspicion of cancer with a previously described system. Distributions of mp-MRI scores were compared across National Comprehensive Cancer Network prostate cancer risk groups. The mp-MRI-identified lesions were compared with the location of positive core needle biopsies to assess mp-MRI localization of true lesions. RESULTS The mp-MRI scoring system identified lesions in 84% (48/57) of the patients, including 100% (12/12) in the high-risk group. Scores assigned to lesions in patients in intermediate- and high-risk groups were statistically higher than those in the low-risk group, with a relative risk of 6.72 (95% confidence interval: 2.32-19.51, p<0.001) of having an aggressive score assigned in high-risk patients compared with the low-risk patients. In comparing the localization data from core needle biopsy, 68% of the patients had an MRI-identified lesion in or within one adjacent sextant of the same prostate hemigland, including 85% of aggressive lesions. CONCLUSIONS Use of mp-MRI at the time of diagnosis can identify intraprostatic lesions and assign suspicion for high-risk disease. These data show that high-risk patients are more likely to have suspicious imaging-identified lesions that correlate to the location of biopsy-proven prostate cancer. At this time, the use of mp-MRI to define focal targets represents a complementary tool to patient evaluation for focal therapy strategies.