MP20-17 NEGATIVE AND EQUIVOCAL PREBIOPSY MULTIPARAMETRIC PROSTATE MAGNETIC RESONANCE IMAGING

Abstract

INTRODUCTION AND OBJECTIVE: Pre-biopsy multiparametric MRI (mp-MRI) are widely performed to indicate the presence or absence of prostate cancer these days. Patients and clinicians often consider deferring a biopsy if the MRI is normal. Our objective was to study the possibility to avoid a prostate biopsy with normal and equivocal mp-MRI and to look for factors which may indicate a clinically significant cancer (csCa). METHODS: Histology outcome of 265 transrectal ultrasound prostate biopsy (TRUS-PB) specimens was evaluated and compared with the pre-biopsy mp-MRI Prostate Imaging Reporting and Data System (PI-RADS) scores 1, 2, 3 and reported normal MRIs. The data were collected retrospectively for 12 months from August 2017. Total number of cancer (Gleason Score (GS) ≥ 3+3), percentage of csCa (defined as GS ≥3+4), maximum cancer core length (MCCL) and the number of positive cores against total cores were studied. Digital rectal examination (DRE) findings and prostate specific antigen density (PSAD) were also evaluated to see the relationship to csCa. RESULTS: Only five of the studied MRIs reported as PI-RADS 1 and none of them showed cancer on biopsy. In total, 21/109 (19.3%) of PI-RADS 2, 8/67 (11.9%) of reported normal MRI and 20/84 (23.8%) of PI-RADS 3 lesions showed cancer. On further study, 9.2%, 9% and 11.9% of them were found to be csCa respectively. In other words, 8.8% (16/181) of csCa were observed with negative MRIs (PI-RADS 1, 2 and normal MRI) at a negative predictive value of 92.2%. Seventy-five (27.3%) patients didn’t have prostate biopsies following their MRI and 73.3% (51/75) of them had benign prostate on DRE. Among those who underwent biopsies, 24.1% of cases resulted in a cancer diagnosis when the prostate felt suspicious, whereas only 14.4% of cancer found when prostate felt benign (p=0.044). Mean PSAD among the benign, GS 3+3 and csCa was 0.14, 0.16 and 0.27 ng/ml/ml respectively (p<0.001). A positive correlation was observed with percentage cancer, MCCL and the number of positive cores in the biopsy specimen against PSAD (p<0.001). The average percentage of cancer in the biopsy specimen for csCa and GS 3+3 was 20.1% and 3.2% respectively. MCCL and percentage of positive cores from the total number of cores were higher in csCa when compared to GS 3+3 (6.5 mm Vs 2.5 mm and 37.9% Vs 12% respectively). These findings suggest a higher volume of cancer with high PSAD and in higher GS. CONCLUSIONS: Since our study has demonstrated 9.8% of csCa with normal and equivocal prebiopsy mp-MRI findings, patients must be warned about this possibility if a biopsy is avoided based on such MRI findings alone. Source of Funding: None.