Focal nodular prostatic peripheral zone enhancement on CT to predict clinically significant (Gleason 4+3 and higher) prostate cancer.

Abstract

173 Background: CTs are insensitive for prostate cancer and inaccurate for local prostate cancer staging. However, enhancing peripheral zone nodules can be seen on a CT, and their significance is uncertain. The purpose of this study was to determine whether focal nodular enhancement within the prostatic peripheral zone on a CT is predictive of clinically significant prostate cancer. Methods: Institutional review board approval was obtained and informed consent waived for this Health Insurance Portability and Accountability Act-compliant retrospective study. Forty-three patients with high-grade prostate cancer (Gleason 4+3 [n=14], 3+5 [n=1], 4+4 [n=1], 4+5 [n=19], 5+4 [n=8]) and 96 with cystoprostatectomy-confirmed low-grade (Gleason 3+4 [n=24], 3+3 [n=23]) or absent (n=49) prostate cancer imaged with contrast-enhanced CT within nine months of histology (median: 18 days) comprised the study population. CT images were reviewed by 10 blinded radiologists (five attendings, five residents) who scored peripheral zone enhancement on a scale of 1 (benign) to 5 (malignant). Focal nodular enhancement was considered malignant. Likelihood ratios (LR) and specificities were calculated. Results: Scores of ‘5’ were strongly predictive of clinically significant prostate cancer (pooled LR+: 9.6 [95% CI: 5.8-15.8]) with rare false positives (pooled specificity: 0.98 [942/960, 95% CI: 0.98-0.99]). Attendings outperformed residents (LR+: 14.7 [95% CI: 5.8-37.2] vs. 7.6 [95% CI: 4.2-13.7]) with similar specificity (0.99 [475/480, 95% CI: 0.98-1.00] vs. 0.97 [467/480, 95% CI: 0.96-0.99]). Conclusions: Focal nodular peripheral zone enhancement on a CT is specific and predictive of clinically significant prostate cancer.