Prostate cancer is a  popular malignant tumor in old males. Serum prostatic specific antigen （PSA）  testing and digital rectal examination (DRE) have been considered the accepted method to screen prostate cancer in early stage. However

an elevated serum level of PSA can be caused not only by prostate cancer

but also by some  benign prostate diseases

such as benign prostatic hyperplasia and prostatitis. Furthermore

a low level of PSA cannot exclude prostate cancer completely. In 2009

the middle-time results of two largest-scale clinical trials (PLCO and ERSPC) in the world provided controversial conclusions of PSA for prostate cancer screening. From then on

the debates on PSA testing have been continued. Although the final conclusion is still unclear

it provides an opportunity to rescan the significance of PSA test.