Cyfra 21-1 (маркер плоскоклеточного рака легких)

CYFRA 21-1 (cytokeratin 19 fragments; CK19 soluble fragments) serum testing assists in the diagnostic evaluation, prognostic assessment, and treatment monitoring of non-small cell lung cancer, with greatest utility in squamous cell carcinoma. The assay also serves as an adjunct marker for colorectal adenocarcinoma and breast carcinoma and supports therapeutic decision-making in metastatic differentiated thyroid carcinoma, particularly when disease is refractory to radioiodine.

Cytokeratin 19 is an intermediate filament protein of epithelial cells. During apoptosis, caspase‑3 cleaves cytokeratin 19, releasing soluble fragments (CYFRA 21-1) into the circulation that can be quantified in serum. Concentrations may rise in several epithelial malignancies, including cancers of the lung, colon, breast, and thyroid. In lung cancer, CYFRA 21-1 is most closely associated with non‑small cell lung cancer (NSCLC), particularly the squamous cell subtype, and can aid in distinguishing NSCLC from small cell lung cancer. Elevated values occur in 57–59% of patients with NSCLC and less frequently in small cell disease, with highest sensitivity in squamous tumors. Levels correlate with tumor burden and carry prognostic information: a high pre‑chemotherapy concentration is unfavorable, whereas a decline greater than 27% during therapy indicates a favorable treatment response. Concurrent elevation of squamous cell carcinoma antigen (SCCA) further supports NSCLC. For colorectal cancer, CYFRA 21-1 may be used alongside CA 19‑9 and carcinoembryonic antigen (CEA) to aid diagnosis, estimate prognosis, and monitor therapy. Higher values are typical of larger tumors, while modest elevations have been associated with better responsiveness to cytotoxic chemotherapy. In thyroid malignancy, the marker can inform management of metastatic differentiated thyroid carcinoma. Markedly increased concentrations are characteristic of aggressive, radioiodine‑refractory disease and are observed most often in papillary carcinoma. In breast oncology, CYFRA 21-1 is elevated in 65% of women with metastatic disease and shows greater sensitivity than CEA or CA 15‑3; combining CYFRA 21-1 with CEA and CA 15‑3 yields an overall sensitivity of approximately 90%. A high pretreatment level is associated with poorer prognosis. Elevations are not specific for malignancy and may occur with chronic renal failure, pulmonary fibrosis, or hepatobiliary disorders; results require interpretation in the context of clinical, laboratory, and imaging findings.