Sextant localization of prostate cancer in peripheral zone by MRI: correlation with systemic biopsy pathology

Objective: To determine the efficacy of sextant localization of prostate cancer (PCa) in PZ (peripheral zone) by MR Imaging. Methods: Fifty-one cases of PCa and 29 cases of benign prostate diseases were enrolled in the study. Each peripheral zone was divided into 6 sections (left/right bottom, middle and tip ) in the same fashion for biopsy and the characteristics of each sextant was evaluated separately. Being blinded to clinical data, 2 radiologists with different subspeciahy experience analyzed MR images of the 480 sections of these 80 cases retrospectively. Each sextant region impression of likelihood for cancer was estimated by the rank of a five-point rating scale (1=definite PCa, 2=probable PCa, 3=possible PCa, 4=probably not PCa, 5=definitely not PCa). If definite PCa was considered, then it was staged furthermore. Each diagnosis of sextant region was compared with the pathological result of corresponding biopsy site. Result: (1) Four hundred and seventy sections (205 cancerous and 265 benign) were proved by biopsy. The diagnosis efficacy was best when cutoff point was 2. There was moderate consistency between the results of MRI and pathology with the kappa value of 0.549-0.560. The total accuracy was 78.1%-78.3% with the sensitivity of 69.3%-76.1% and the specificity of 84.9%-80.0%. The positive predictive value was 78.0%-74.6% and the negative predictive value was 78.1%-81.2%. (2) The ROC analysis demonstrated that Az with total impression recorded by two readers had not significant difference(0.829±0.020 vs. 0.840±0.019, U=-0.3988, P>0.05). Conclusion: MRI may be an elementary way to localize PCa in PZ, but the diagnosis efficacy need to be improved furthermore. (authors)