https://www.healthday.com/health-news/men-health/psa-test-a-thing-of-the-past-518850.html
“The prostate-specific antigen (PSA) test is not reliable as a screening tool for cancer, Thomas A. Stamey, M.D., of Stanford University, who first developed the test in 1987, says in the October issue of the Journal of Urology.”
I don’t know anyone who would rely on PSA testing as their sole source for a cancer diagnosis, but - depending on the results, especially comparing more than one test (i.e., PSA velocity) - it’s certainly a useful indicator for further investigation.