A lower PSA does not necessarily mean that the disease will not progress, and chemotherapy is only a means of controlling the progression of the disease, not a cure. PSA is an important indicator for diagnosing prostate cancer and determining disease progression. When local recurrence or distant metastasis occurs, PSA changes usually appear several years earlier than imaging changes. Therefore, changes in PSA can be used to judge the effect of treatment and detect recurrence and metastasis in time. A decrease in PSA after chemotherapy for prostate cancer usually suggests that chemotherapy is effective for the lesions, but is not able to completely control the progression of the disease. However, a few patients may have new metastatic lesions, or previously undetected tiny metastatic lesions are found after increasing in size; in addition, a few patients may be combined with other tumors or diseases, which need to be combined with puncture biopsy to determine whether they are real metastatic lesions. It is recommended that when PSA is reduced after chemotherapy for prostate cancer but there is proliferation, timely medical treatment should be sought to avoid delaying the condition.