What are tumor markers?
Tumor markers are blood tests for substances elevated in some cancers. Common ones: PSA (prostate), CA-125 (ovarian), CA 19-9 (pancreatic), AFP (liver, testicular), CEA (colon), beta-HCG (testicular, gestational).
Limitations are important: tumor markers aren't typically used to diagnose cancer (false positives are common in non-cancer conditions). They're more useful for tracking response to treatment and monitoring for recurrence after treatment.
Baseline levels before treatment, mid-treatment, and post-treatment trends are the meaningful framing — not single values. Bring all your tumor marker values, not just the most recent.
This answer is general information, not medical advice. Your own doctor should confirm what applies to your case.