How is PSA used to monitor prostate cancer?

In the first part of our series, we described how PSA is used as a screening tool to help detect prostate cancer in men who don’t have symptoms. PSA screening can save lives, but it frequently finds slow-growing cancer that might not ever become deadly. Sometimes PSA rises for reasons unrelated to cancer, including inflammation in the prostate, or a benign enlargement of the gland that often occurs with age. There are longstanding concerns that PSA screening leads to unnecessary tests and overdiagnosis of prostate cancer.

Doctors also measure PSA to check for disease progression in men who have an established cancer diagnosis. But where PSA screening often yields ambiguous findings, using PSA to monitor cancer progression “is one of the most useful tools we have,” says Dr. Marc B. Garnick, the Gorman Brothers Professor of Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center, and editor-in-chief of the Harvard Medical School Guide to Prostate Diseases.

Men on active surveillance for low-risk prostate cancer might need treatment if their PSA levels start to rise. Doctors also measure PSA to check for recurring cancer in men who were already treated with surgery or radiation. But use of the test in such cases differs in important ways