MRI assessment of pathological stage and surgical margins in anterior prostate cancer (APC) using subjective and quantitative analysis

Purpose To evaluate magnetic resonance imaging (MRI) for assessment of extraprostatic extension (EPE) and positive surgical margins (PSM) in anterior prostate cancer (APC). Materials and Methods With Institutional Review Board approval, 25 APC (>2/3 of tumor anterior to urethra) were assessed using 3T MRI by two blinded radiologists for: size and maximal leading edge of tumor (relative to anterior fibromuscular stroma [AFMS]) on b ≥1000 sec/mm2 echo-planar-MRI fused onto T2-weighted-MRI, invasion of AFMS and EPE. Comparisons were performed between APCs by EPE/PSM using chi-square, multivariable analysis, and receiver operator characteristic (ROC) analysis. Results The prevalence of EPE and PSM were 52% (13/25) and 36% (9/25). Tumor sizes were larger with EPE (22.5 ± 8.4 vs. 14.7 ± 6.3, P = 0.02) and PSM (23.0 ± 9.3 vs. 16.4 ± 7.0, P = 0.06). Area under ROC curve (AUC-ROC) for the diagnosis of EPE by tumor size was 0.77 (95% confidence interval [CI] 0.58–0.95); ≥16 mm size = sensitivity/specificity 69.2/66.7%. Maximal leading edge of tumor was greater with EPE (2.4 ± 2.2 vs. –0.2 ± 3.0) and PSM (2.8 ± 2.3 vs. –0.3 ± 2.5), (P = 0.023, 0.031). AUC-ROC for diagnosis of EPE/PSM by leading edge was 0.78 (CI 0.57–0.97) and 0.75 (CI 0.56–0.94). A ≥1 mm leading edge yielded sensitivity/specificity of 76.9/75.0% and 77.8/62.5% for diagnosis of EPE/PSM. 60–72% (15–18/25) tumors invaded AFMS (k = 0.74), which was not associated with EPE/PSM (P = 0.12–0.14). Radiologists' assessment of EPE had sensitivity/specificity of 61.5–69.2/50.0–75.0% (k = 0.53). Conclusion Tumor size and leading edge of tumor relative to AFMS may enable diagnosis of EPE and positive surgical margins in APC. Level of Evidence 2 J. Magn. Reson. Imaging 2016