Detection of prostate cancer: Utility of diffusion-weighted MR imaging and 3D MR spectroscopic imaging

Abstract

PurposeTo prospectively compare the mean ADC generated from DWI, the mean choline+creatine/citrate ratio generated from 3D MRS and the combined mean ADC and mean choline+creatine/citrate ratio in the detection of prostate cancer, and to correlate between the choline+creatine/citrate ratio and the aggressiveness of malignancy determined by Gleason score, with histopathological examination of the excised gland as the reference standard. Patients and methodsForty-six patients with biopsy-proved cancer underwent pre-operative MRI at 1.5T. Axial T1, axial, coronal and sagittal T2-weighted, diffusion-weighted and 3D MRS using a point-resolved spectroscopic sequence (PRESS) were acquired. The mean ADC, mean choline+creatine/citrate ratio and combined parameters for malignant lesions are correlated with the pathological results. For each malignant lesion choline+creatine/citrate ratio was correlated with the aggressiveness of malignancy determined by Gleason score. Receiver operating characteristic (ROC) curves were used to determine sensitivity, and specificity of the studied parameters, and Kappa measures of agreement were calculated for prostate cancer detection. ResultsThe mean ADC for tumor tissue was 1.0±0.22×10−3mm2/s (mean±SD), and was significantly lower than that for non-tumor tissue 1.44±0.28×10−3mm2/s (p<0.001). For MRS study the mean (choline+creatine)/citrate ratio in tumor tissue was 1.98±1.0, and was significantly higher than that for non-tumor tissue, 0.72±0.39 (p<0.001). By combining both ADC values and (choline+creatine)/citrate ratio for differentiating malignant from non-malignant tissues a receiver operating characteristic analysis (ROC) curve showed Area under curve (AUC=0.93) and was significantly higher than either (choline+creatine)/citrate ratio alone (AUC=0.86) (p<0.001) or ADC value alone (AUC=0.89) (p<0.001). There is an increasing (choline+creatine)/citrate ratio with increasing Gleason score, however, there is overlap between groups. A greater sensitivity of MRS for tumor detection 85% and 92% was present for tumors with Gleason score 4+3 and ⩾4+4, respectively, while for tumors with Gleason score 3+3 the sensitivity was 63%. ConclusionThe combination of ADC and (choline+creatine)/citrate ratio is better than each parameter alone in differentiating between tumor and non-tumor prostatic tissue, also MR spectroscopic imaging findings of prostate tumor (Cho+Cr)/Cit ratio correlate with pathologic Gleason score. The combined parameters offer a promising non-invasive method for the diagnostic workup of prostate cancer.