PSA is the most argued-over test in urology. A single number rarely settles anything.
What PSA is
Prostate specific antigen is a protein made by prostate cells, and its actual job has nothing to do with cancer: it is the enzyme that liquefies semen after ejaculation so sperm can swim, which makes PSA, of all things, an enzyme that helps get a woman pregnant. It rises with age, with prostate enlargement, with inflammation, and with cancer. It also bumps up temporarily after a digital rectal exam, after ejaculation, and after bike riding.
That last list is the whole problem. PSA is prostate specific. It is not cancer specific.
Why one number is not enough
A cutoff of 4.0 was chosen decades ago as a compromise, and one number for every man does not work. Age-based ranges, free versus total PSA, and PSA density all add information a single value cannot.
PSA density has become more useful than it used to be, because MRI now gives an accurate prostate volume as a matter of course.
What happens after an elevated result
This is the part that has changed most. An elevated PSA no longer sends you straight to biopsy. The usual next step is an MRI of the prostate. A reassuring MRI can mean no biopsy at all. A suspicious one lets us aim at the area of concern rather than sampling blindly.
Secondary markers can further refine the odds before anyone commits to a biopsy, including PHI, SelectMDx and the 4Kscore. When a biopsy is warranted, more are now done through the perineum rather than the rectum, which lowers infection risk.
And if it is cancer
The old argument against screening rested on overtreatment, and it is much weaker now. Low risk prostate cancer today is usually watched rather than treated, with periodic PSA, imaging and repeat biopsy, and treatment held back for cancers that show they need it. That is called active surveillance, and it broke the link between finding a small cancer and having an operation you did not need.
Where screening guidance stands
In 2012 the U.S. Preventive Services Task Force recommended against PSA screening for all men. In 2018 that was revised to shared decision-making for men aged 55 to 69. For most men, screening every one to two years from about age 50 to 69 is reasonable, earlier with a family history, African American ancestry or known genetic risk.
Given my experience, I tend to start a little earlier than the guidance, and I continue to actively screen as long as a man has a reasonable life expectancy and is reasonably healthy.