News that Joe Biden has advanced prostate cancer has revived long-standing questions about the benefits versus the harms of a blood test that screens for the most commonly diagnosed cancer among men in the U.S.

Prostate-specific antigen, or PSA, screening tests are an imperfect tool for detecting prostate cancer, doctors and public health experts say.

Part of the problem is identifying and treating aggressive cancers like Biden’s while not unnecessarily treating men with slow-growing cancers unlikely to sicken them. Autopsies found the disease to be so widespread that more than one-third of white men and half of Black men in their 70s had prostate cancers that would never do any harm.