Objective: The aim of this study was to evaluate three indirect MRI signs for predicting extraprostatic disease in patients referred to radical prostatectomy: index tumor volume (MTV), apparent diffusion coefficient (ADC) and tumor contact length (TCL).
Materials and methods: This prospective study included 183 patients with biopsy proven prostate cancer. In all patients the MTV (ml), ADC (× 10-5 mm2/s) and TCL (mm) of the index tumor were registered at the preoperative MRI. Whole-mounted microscopical examination classified each patient as having either localized- or extraprostatic disease. The Youden index was used to identify the optimal cut-off values for predicting extraprostatic disease. Univariate regression analyses were conducted to estimate the odds ratio (OR) with 95% confidence intervals (CI). Results were stratified upon zonal location of the index tumor.
Results: Extraprostatic disease was identified in 103 (56%) patients. The risk of extraprostatic disease was nine times higher in peripheral zone tumors with ADC ≤ 89 (OR 9.1, 95% CI 4.2-19.6), five times higher in MTV ≥ 0.9 ml (OR 5.5, 95% CI 2.6-11.4) and five times higher in case of TCL ≥ 14 mm (OR 4.9, 95% CI 2.3-10.2). None of the indirect MRI signs could predict extraprostatic disease for transition zone tumors.
Conclusion: The MTV, ADC and TCL are all significant predictors of extraprostatic disease for peripheral zone tumors, while none of the indirect signs were useful for transition zone tumors.
Keywords: ADC; Extraprostatic disease; Indirect signs; MRI; Prostate cancer; Staging; Tumor capsule length; Tumor contact length; Tumor volume.