Finally, receiver operating characteristic (ROC) curves revealed that, although Proteobacteria failed to distinguish prostate cancer from BPH, it had better potential in predicting distant metastasis than PSA level (tended to be higher in patients with metastatic prostate cancer) (area under the ROC curve, 0.860; p < 0.001) (Fig. 6E). This evidence concerns the gene KLK3 and prostate cancer.