Login to Access Video or Poster Abstract: MP08-17
Sources of Funding: none

Introduction

Focal ablation during high intensity Focused ultrasound (HIFU) offers reduced comorbidities, but increased risk of untreated disease. Magnetic resonance imaging (MRI) is increasingly being used to select patients for focal HIFU. Our objective was to characterize how well MRI fusion biopsy identifies disease within the prostate by studying men who have underwent a MRI fusion biopsy and subsequent radical prostatectomy.

Methods

A prospective database was queried for a history of radical prostatectomy and MRI fusion biopsy. Men underwent a 3 Tesla multi-parametric MRI, one of two radiologists evaluated all MRI scans, and lesions were scored from 1-5 using an institution specific system. A genitourinary pathologist reviewed all prostatectomy specimens and primary and secondary lesions were reported. Differences between MRI lesions and prostatectomy tumor foci were assessed for size, Gleason score, and laterality. Means were compared using students t-test and all statistical analysis was performed using Stata 13.1.

Results

Fifty-eight patients underwent MRI-fusion and 12-core biopsy followed by prostatectomy with a total of 702 biopsy cores evaluated. The median (IQR) age = 66.4years (60-70), PSA = 9.3ng/mL (6-15), and number of prior biopsies = 1 (0-2). Final Gleason score was as follows: 6= 2(3%), 7= 46(79%), and 8-9= 10(17%). There were a total of 120 MRI lesions with a median (range) of 2 (1-5) marked for fusion biopsy per patient, and a mean of 2.4 fusion biopsies per lesion. A MRI lesion was found in the quadrant of the primary (largest) surgical pathologic focus in 45/58 (78%). However, of these MRI lesions only 24 (53%) had matching grade with 12 benign biopsies being upgraded to Gleason ≥7 on surgical pathology. The mean MRI lesion greatest dimension was 1.9cm compared to 2.2cm on final pathology (p=0.03). MRI lesions were similar in size to final pathology (not more than 1cm smaller) in 37/45 (82%) while 3 (7%) were 1-1.9cm smaller and 5 (11%) were ≤2cm smaller. A total of 23/58 (40%) had fusion biopsy Gleason ≤7 on a single side, and on final pathology 14 (61%) had a secondary focus of bilateral disease.

Conclusions

A significant number of surgical specimens contained lesions larger than predicted by MRI or had bilateral disease when only unilateral disease was seen on biopsy. When considering focal HIFU, it would be prudent to treat a larger area surrounding the dominant MRI lesion. Furthermore, follow-up biopsies of the contralateral untreated lobe are imperative.

Funding

none