Low-risk prostate cancer: the accuracy of multiparametric MR imaging for detection.

Abstract

To retrospectively determine diagnostic performance with multiparametric magnetic resonance (MR) imaging for detection of cancer of different tumor volumes and Gleason grades in patients with clinically low-risk prostate cancer. The local ethical committee and institutional review board approved this study. Consecutive patients with clinically determined low-risk cancer (n = 100) were examined with multiparametric MR imaging (T2 weighted, diffusion weighted, and dynamic contrast material enhanced) by using a 3.0-T imager before prostatectomy. Two radiologists independently assessed the likelihood of cancer per sextant. Cancers with a volume of 0.5 cm(3) or more identified at histopathologic examination were compared with multiparametric MR images. Cancer detection with multiparametric MR imaging was assessed for tumors of different volumes and Gleason grades by using a logistic generalized estimating equation model with 95% confidence intervals (CIs) with two optimal dichotomized cutoff scores. For cancers greater than or equal to 0.5 cm(3), with respect to cancer volume and Gleason grade, multiparametric MR imaging showed high diagnostic performance for the detection of cancer. Diagnostic accuracy with multiparametric MR imaging was significantly higher for cancers with a volume greater than 1 cm(3) than for those with a volume of 0.5-1 cm(3) (87.7%; 95% CI: 82.4%, 94.3% vs 82.6%; 95% CI: 79.0%, 88.7%; P = .02) and for cancers with Gleason grades of 7 or more than for those with grades of 6 or less (89.2%; 95% CI: 85.4%, 93.8% vs 80.6%; 95% CI: 71.2%, 89.8%; P = .01). Detection rates for cancers with a volume more than 1 cm(3) and a Gleason grade of 7 or more were significantly higher than for those with a volume of 0.5-1 cm(3) and a Gleason grade of 6 or less(87.8%; 95% CI: 85.3%, 93.7% vs 82.0%; 95% CI: 75.6%, 86.1%; P = .01). Detection of prostate cancer in patients with clinically low-risk cancer with multiparametric MR imaging is highly accurate, and larger cancer volume and higher Gleason grade are associated with higher detection accuracy.