CYFRA 21-1 is a tumor marker — a fragment of cytokeratin 19 — often elevated in non–small cell lung cancer, particularly squamous cell carcinoma. It helps assess prognosis and monitor treatment response but is not definitive for diagnosis or screening. Levels can also rise with benign lung diseases, liver or kidney dysfunction, and other cancers, so results require clinical and imaging correlation.

CA125 (cancer antigen 125) is a blood tumor marker primarily associated with ovarian cancer but can be elevated in some lung cancers, especially adenocarcinomas and those with pleural involvement. It is non‑specific—levels can rise in benign conditions—and is not used for screening or definitive diagnosis. In lung cancer, CA125 may reflect advanced disease or pleural spread and can help monitor treatment response.

CYFRA 21-1 has moderate diagnostic accuracy: sensitivity roughly 40–70% (higher in squamous‑cell lung cancer) and specificity often 80–90%. It’s more useful for prognosis and monitoring treatment or recurrence than as a screening or standalone diagnostic test. Levels can also rise in benign lung disease and smokers, so results require correlation with clinical assessment and imaging.

There is no single definitive marker for lung cancer. Blood tumor markers commonly used are CEA, CYFRA 21‑1, NSE and SCC antigen for detection and monitoring. Molecular markers (EGFR mutations, ALK/ROS1 rearrangements and PD‑L1 expression) guide prognosis and targeted therapy. Imaging and tissue biopsy remain necessary for diagnosis and confirmation.

A commonly used normal range for CYFRA 21-1 is up to about 3.3 ng/mL, though some laboratories use lower cutoffs (around 1.8–3.3 ng/mL). Values above the lab-specific reference may suggest epithelial malignancy—particularly non‑small cell lung cancer—but results must be interpreted alongside clinical findings and other investigations. Always use the reference range printed on your test report.

There's no single best blood marker for lung cancer. Diagnosis relies on imaging and tissue biopsy with histology. Serum markers like CYFRA 21‑1, CEA (non‑small cell) and NSE or ProGRP (small‑cell) can aid monitoring but lack diagnostic accuracy alone. Molecular markers (EGFR, ALK, ROS1, PD‑L1) from tumor tissue are crucial for targeted therapy selection and prognosis.