Historically, which prostate cancer biomarker has been largely replaced by PSA measurement?

• A. Alanine aminotransferase
• B. Acid phosphatase
• C. Creatine kinase
• D. Gamma-glutamyltransferase

Answer: (B)

Historically, markers used to track prostate cancer were tied to what the tumor produced in the body. Prostatic acid phosphatase was the standard test for many years because it could reflect the presence and progression of prostate cancer, especially in cases with bone involvement. But PSA, a protein produced almost exclusively by prostate tissue, turned out to be far more specific to the prostate and, crucially, more sensitive. This means PSA rises earlier in disease and provides clearer signals for detecting recurrence or monitoring response to treatment. Because of these advantages, PSA measurement has largely supplanted prostatic acid phosphatase as the main prostate cancer biomarker.

The other enzymes listed are not tied to prostate cancer. Alanine aminotransferase, gamma-glutamyltransferase, and creatine kinase are associated with liver, biliary/other organ systems, and muscle, respectively, and are used for different diagnostic purposes rather than prostate cancer monitoring.