Is PI-RADS 3/total lesion ratio associated with clinically-significant prostate cancer in patients with equivocal-risk lesions on multi-parametric MRI?

Abstract

149 Background: Prostate imaging reporting and data system (PI-RADS) category 3 (P3) provides an equivocal assessment of prostate cancer (PCa). We aimed to investigate imaging parameters including the ratio of P3-to-total regions of interest (ROI) that may assist in identifying P3 lesions harboring clinically-significant PCa (csPCa). Methods: We retrospectively queried our institutional MRI-ultrasound fusion biopsy database to identify patients without a prior diagnosis of PCa and with at least one P3 lesion on multi-parametric MRI (mpMRI) who underwent fusion biopsy during Feb 2015-Oct 2017. mpMRI findings were assessed, including prostate and P3 volumes, number of ROIs, and P3-to-total ROIs ratio (P3 lesion volume/total ROIs volumes). Logistic regression and area under the curve (AUC) were used to assess the ability of clinical and mpMRI characteristics to predict csPCa, defined as any grade group (GG)≥2 cancer or GG 1 cancer in > 2 cores or > 50% of any positive core from targeted biopsy of the P3 lesion. Results: Of 127 men with at least one P3 lesion, 29 (22.8%) had csPCa on the biopsy of P3 lesions. Patients with csPCa in P3 lesions had smaller prostate volumes (42.1mL vs 56mL, p = 0.003), lower P3/total ROIs ratios (0.46 vs 1.00, p < 0.001), and higher numbers of total ROIs (2 vs 1, p = 0.004). Compared with patients who had a P3/total ROIs ratio > 0.58, men with ratios < 0.58 were more likely to be diagnosed with csPCa in a P3 lesion (57.1% vs 9%, p < 0.001). Using a threshold of 0.58, P3/total ROIs ratio was 76.1% sensitive and 80.6% specific for csPCa in a P3 lesion. On multivariate analysis, smaller prostate volume (OR1.04, 95%CI 1.01-1.07, p = 0.01) and lower P3/total ROIs ratio (OR1.04, 95%CI 1.02-1.07, p = 0.003) were associated with an increased risk of csPCa in P3 lesions. P3/total ROIs ratio (AUC 0.73) and prostate volume (AUC 0.70) were superior to PSA density (AUC 0.65) for the prediction of csPCa in P3 lesions. Conclusions: Our data indicated that prostate volume and P3/total ROIs ratio outperformed PSA density in and were associated with detecting csPCa in P3 lesions. P3/total ROIs ratio could be used to avoid 80.6% of unnecessary biopsies of a P3 lesion in men with multiple ROIs.