Central zone lesions on magnetic resonance imaging: Should we be concerned?

INTRODUCTION AND OBJECTIVE: The Prostate Imaging Reporting and Data System (PI-RADS) score was developed to evaluate lesions in the peripheral and transition zone on multiparametric magnetic resonance imaging (mpMRI) of the prostate. We aim to determine if the PI-RADS scoring system can be used to evaluate central zone lesions on mpMRI.

MATERIALS AND METHODS: A retrospective review of 73 patients who underwent mpMRI/ultrasound (US) fusion-guided biopsy of 143 suspicious lesions between February 2014 and October 2015 was performed. All patients underwent a 3T mpMRI. Indications for mpMRI included an abnormal digital rectal examination, PSA velocity >0.75ng/dl/y, and patients on active surveillance. The mpMRI sequence involved T2-weighted imaging, diffusion-weighted imaging, and dynamic contrast enhancement. Using 3-dimensional model software (Invivo Corporation, Gainesville, FL, USA), a minimum of 3 magnetic resonance imaging (MRI)/US fusion-guided biopsy samples were taken from each prostate lesion seen on mpMRI irrespective of PI-RADS score, using local anesthesia in an outpatient clinic setting.

RESULTS: A total of 73 patients underwent MRI/US fusion-guided biopsy of 85 peripheral zone lesions, 31 transitional zone lesions, and 27 central zone lesions. Only 2 (7%) of central zone lesions were positive for prostate cancer. Both patients had lesions which were graded as PI-RADS 3. Both the patients had multifocal lesions that encompassed≥50% of the central and transition zones on the sagittal view MRI images. Both patients previously had transrectal US-guided biopsy of the prostate which was negative for cancer. Both patients underwent a robotic-assisted laparoscopic prostatectomy, each revealing high-grade cancer.

CONCLUSIONS: Lesions involving only the central gland/zone seen on MRI are less concerning for malignancy and should not be given equal weight as peripheral zone lesions. In this series, no lesions involving solely the central gland/zone, regardless of PI-RADS score, was positive for malignancy on MRI/US fusion-guided biopsy. Consideration of a modified PI-RADS scoring system should be given to help identify central zone lesions with malignant potential.