Accuracy of Prostate Multiparametric MRI in Identification of Intraprostatic Tumor Deposits Validated on Transperineal Biopsies

Abstract

To determine the accuracy of prostate multiparametric (mp) MRI in identification of intraprostatic tumor deposits using a systematic and targeted MR-guided transperineal prostate biopsy technique as a reference.One hundred sixty patients underwent a combined systematic and targeted MRI-guided prostate biopsy using a transperineal approach under general anesthesia. For each patient, a pre-biopsy mpMRI scan was obtained and imported into a prostate biopsy planning system. Transverse images were then reoriented from the supine to dorsal lithotomy position. Dividing the prostate into an apical and base section, a systematic array of transperineal biopsies spaced approximately 10mm apart was planned with additional biopsies targeting mpMRI-identified PI-RADS 3, 4 or 5 lesions. Biopsy procedures were carried out in the dorsal lithotomy position using a transrectal ultrasound with stepper-stabilizer and template grid. Matching of the planning mpMRI images to live ultrasound images was achieved using the template grid as a reference.All patients successfully underwent their biopsy procedure as planned. An average of 26 biopsy specimens were obtained per patient (range 11-44). Twenty-nine percent (15/52) of PI-RADS 3 lesions, 49% (46/94) of PI-RADS 4 lesions, and 76% (39/51) of PI-RADS 5 lesions were pathologically confirmed prostate cancer. Forty-two percent (67/160) of patients harbored mpMRI-unidentified prostate cancer. Twenty-two percent (36/160) of patients harbored mpMRI-unidentified GS≥7 disease and four percent (7/160) of patients harbored mpMRI-unidentified GS≥8 disease.Using prostate mpMRI to identify intraprostatic tumor deposits without pathologic confirmation would lead to significant numbers of false positive mpMRI identified lesions and miss clinically significant prostate cancer outside of mpMRI identified lesions in over 20% of patients. Use of systematic prostate biopsy information appears necessary to significantly improve the accuracy of mpMRI identification of intraprostatic tumor deposits.