Prostate cancer is the most common malignant tumor in men in western countries, accounting for the 2nd cause of death from malignant tumors. In recent years, the incidence of prostate cancer in China is also on the rise and now ranks 6th in the incidence of malignant tumors in men in China. Statistics show that the proportion of patients with mid- to late-stage prostate cancer in China is significantly higher than in Europe and the United States, which has a direct impact on the treatment outcome and long-term survival of prostate cancer patients in China. Early stage prostate cancer usually has no typical symptoms. When symptoms such as difficulty in urination, hematuria, bone pain and anemia appear, it often indicates that the cancer is in advanced stage. How can prostate cancer be detected early? The following is an introduction to PSA (Prostate Specific Antigen), a common clinical tool for early screening. 1. It is an enzyme that helps restore coagulated semen to a liquid state and is associated with male fertility. Professor William J. Catalona, a world-renowned urologist, is known as the “father of PSA for prostate cancer” because he was the first to discover that the PSA test could be used for first-line screening of prostate cancer. His 36,000-person census study in St. Louis (Missouri, USA) led to the approval of the PSA test and the fPSA test by the FDA. 2. Why PSA is needed Serum PSA is currently recognized as a specific marker for prostate cancer and can be used for screening and early diagnosis of prostate cancer. Under normal circumstances, there is a dense basement membrane underneath the prostate epithelial cells, which acts as a “high wall” separating the epithelial cells from the blood. As a result, almost all PSA can only enter the semen through the ducts, but not the bloodstream. Therefore, the serum PSA concentration in normal men is very low, while the semen PSA concentration is about one million times higher than the serum PSA concentration. When you have prostate disease, the basement membrane is damaged to varying degrees, especially in the case of prostate cancer, the abnormal growth of cancer cells can cause serious damage to the basement membrane, allowing PSA to enter the bloodstream through this “abnormal pathway”. The concentration of PSA in the lumen of the prostate is much higher than in the blood, resulting in a significant increase in serum PSA levels. The PSA test is a convenient way to screen for prostate tumors in patients with suspected prostate enlargement. 2 ml of blood is required for the PSA test and there is no need to fast before the test. The PSA test is a very convenient way to screen for prostate cancer. It is generally believed that the normal value of serum PSA is (0~4)ng/ml, but there may be slight differences among hospitals according to their own standards of examination instruments and different reagents used. When the serum PSA (tPSA) is >10ng/ml, prostate cancer should be highly suspected, alerted and promptly seen by a urologist, and if necessary, a prostate magnetic resonance imaging (MRI) examination and prostate puncture biopsy should be performed to further clarify the presence of prostate cancer. When tPSA is between 4~10ng/ml, the possibility of prostate cancer is about 25% (in Europe and America). The clinical term of 4~10ng/ml as the gray zone of PSA refers to the fact that it is difficult to determine whether a patient is likely to have prostate cancer when the PSA is in this range. At this point, it is recommended to refer to PSA-related variables: free PSA (fPSA), PSA density (PSAD), and PSA rate (PSAV). These parameters will not be described in detail here due to their relative complexity.