Medically Reviewed by: Dr. Dipak Ladda, M.D.
Expertise: Consultant Pathologist
Last Updated: July 25, 2026
Medical Analysis
Comprehensive Clinical Overview and Optimization Guide for Cyfra 21-1 Lung Cancer Marker in Oncology
Introduction to Cyfra 21-1 Biomarker and Global Lung Cancer Epidemiology
Lung cancer is the leading cause of cancer death worldwide (18.0% of all cancer deaths) and caused an estimated 1.8 million deaths in 2020. CYFRA 21 – 1, a fragment of cytokeratin 19, was identified as a sensitive marker for lung cancer and is commonly used in the management of non-small cell lung cancer [9]. It is released into circulation either due cell death or after tumour lysis [9]. It is soluble in serum and easily identifiable as a CTC [9]. An elevated CYFRA 21 – 1 level has been proposed as a negative prognostic indicator in non-small cell lung cancer [4].
Clinical Indications and Diagnostic Guidelines
| Indications | Description |
| Non-Small Cell Lung Cancer (NSCLC) | Diagnosis, prognosis, treatment monitoring [2] |
| Detection of Relapse | Monitoring disease recurrence after therapy [5] |
| Prognostic Evaluation | Assesses tumor burden, stage, and survival outlook [4] |
| Other Cancers | Monitoring liver metastases, cervical, esophageal, head & neck cancers [3, 8] |
| Differential Diagnosis | Helps distinguish malignant vs benign lung lesions [10] |
Advanced Laboratory Methods of Detection and Electrochemical Analysis
Chemiluminescence immunoassay. ELISA. Electrochemiluminescence. Electrochemical detection of Cyfra 21-1 utilizes components like MPA, Ab1, BSA, EDC/NHS, DPV, NCA-Fc, ROP, C3H4O, and Ab2.
Sample Collection, Storage, and Pre-Analytical Protocols
Collect 3 mL of plain blood in red or serum separator tube. Allow specimen to clot completely at room temperature. Separate serum from cells as early as possible or within 2 hours of collection. Storage/Transport Temperature: Refrigerated. Stability: After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 2 months.
Comprehensive Reference Interval and Demographic Breakdown Tables
| Category | Reference Range (ng/mL) |
| Overall | 0.66 – 3.84 [10] |
| Men | 0.68 – 4.09 [10] |
| Women | 0.60 – 3.62 [10] |
| Age 20-40 | 0.62 – 3.28 [10] |
| Age 41-50 | 0.64 – 3.72 [10] |
| Age 51-60 | 0.74 – 4.36 [10] |
| Age > 60 | 0.96 – 5.00 [10] |
Serum Levels and Clinical Condition Interpretation Tables
| Cyfra 21-1 Level (ng/mL) | Interpretation | Possible Clinical Condition |
| Less than 3.3 ng/mL | Normal | No evidence of malignancy [10] |
| 3.3 – 10 ng/mL | Mild elevation | May occur in early-stage malignancy or benign lung disease (COPD, pneumonia, pulmonary fibrosis) [10] |
| Greater than 10 ng/mL | Significantly elevated | Strongly suggests epithelial malignancy (especially squamous cell carcinoma of lung) [6, 10] |
| Greater than 20 ng/mL | Markedly elevated | Advanced or metastatic squamous cell carcinoma [6] |
| Greater than 50 ng/mL | Very high | Extensive tumor burden or recurrence post-therapy [5, 6] |
False Positive Conditions and Confounding Variables
Liver disease. Renal failure. Extrapulmonary malignancies. Mesothelioma. COPD. Pneumonia. Pulmonary fibrosis.
Interfering Laboratory Factors
Icteric serum sample. Lipemic serum sample. Haemolyzed serum sample.
Clinical Applications and Disease Monitoring Framework
| Clinical Application | Key Point |
| Diagnosis | Marker for squamous NSCLC and other epithelial cancers [7] |
| Prognosis | High levels indicate advanced disease or poor outcome [4] |
| Therapy Monitoring | Fall in levels shows good treatment response [5] |
| Recurrence Detection | Rising levels suggest relapse or metastasis [5] |
| Differential Diagnosis | Helps distinguish malignant vs benign lung lesions [10] |
| Combined Marker Use | Enhances accuracy with CEA, NSE, or SCC antigen [7] |
| Screening | Not recommended for general population screening [10] |
Comparative Analysis of Lung and Tumor Biomarker Panels
| Marker | Sensitivity | Specificity | Notes |
| CEA | 56.7 percent | Moderate | Highest sensitivity among single markers [7] |
| NSE | Moderate | 93.3 percent | Highest specificity among single markers [7] |
| CYFRA 21-1 | 75 to 80 percent | 85 to 90 percent | Especially useful in squamous cell carcinoma & NSCLC [6, 7] |
| Marker Panel (EGF, SCD26, CAL, CEA) | 91.7 to 97 percent | 40 to 45 percent | High sensitivity using multi-marker combination |
| Autoantibody Panels | 75 to 98 percent | 85 to 97 percent | Emerging for early diagnosis using serum profiles |
For Non-Medicos
Understanding Your Cyfra 21-1 Lung Marker Test Made Simple
What Is Cyfra 21-1 and Why Do Doctors Order It?
Cyfra 21-1 is a protein fragment that enters the bloodstream when certain lung cells break down or when tumors are present [9]. Doctors primarily use this blood test to help manage non-small cell lung cancer, track how well treatments are working, check for disease return, and evaluate overall prognosis [2, 4, 5].
What Do Your Test Results Mean?
Test values are measured in nanograms per milliliter (ng/mL), with an overall normal range typically falling between 0.66 and 3.84 ng/mL [10]. Mild elevations can sometimes occur due to non-cancerous conditions like pneumonia or COPD, while significantly higher numbers strongly suggest lung tumors or advanced epithelial malignancies [6, 10].
Can Other Conditions Cause High Scores?
Yes, high marker levels do not always mean cancer [10]. Conditions such as severe liver disease, kidney failure, chronic bronchitis, pneumonia, pulmonary fibrosis, and mesothelioma can also cause unexpected elevations. Furthermore, bad sample quality like hemolyzed or icteric blood can interfere with accurate lab testing.
How Is the Test Performed and Monitored?
A small blood sample is collected in a plain red-top tube, and the clear serum is separated quickly to maintain stability. Doctors track these numbers over time; falling levels usually indicate successful treatment, while rising levels can warn of a potential relapse or spread [4, 5].
References:
Nakao, M., Kinoshita, R., Kuriyama, M., Kiyotoshi, H., Sugihara, M., Takeda, N., Ohtakara, K., & Muramatsu, H. (2024). Serum CYFRA 21-1 level as a prognostic marker for extensive disease small cell lung cancer. Anticancer Research, 44(2), 845–851. https://doi.org/10.21873/anticanres.16877
Miyadera, K., Kakuto, S., Sugai, M., Tsugitomi, R., Amino, Y., Uchibori, K., Yanagitani, N., Sugiura, H., Seike, M., Nishio, M., & Ariyasu, R. (2024). Serum CYFRA 21-1 as a prognostic marker in non-small-cell lung cancer patients treated with immune checkpoint inhibitors. Cancers, 16(21), 3712. https://doi.org/10.3390/cancers16213712
Liu, L., Xie, W., Xue, P., Wei, Z., Liang, X., & Chen, N. (2019). Diagnostic accuracy and prognostic applications of CYFRA 21-1 in head and neck cancer: A systematic review and meta-analysis. PLOS ONE, 14(5), e0216561. https://doi.org/10.1371/journal.pone.0216561
Yu, Z., Zhang, G., Yang, M., Zhang, S., Zhao, B., Shen, G., & Chai, Y. (2017). Systematic review of CYFRA 21-1 as a prognostic indicator and its predictive correlation with clinicopathological features in non-small cell lung cancer: A meta-analysis. Oncotarget, 8(3), 4043–4050. https://doi.org/10.18632/oncotarget.14022
Holdenrieder, S., Wehnl, B., Hettwer, K., Simon, K., Uhlig, S., & Dayyani, F. (2017). Carcinoembryonic antigen and cytokeratin-19 fragments for assessment of therapy response in non-small cell lung cancer: a systematic review and meta-analysis. British Journal of Cancer, 116(8), 1037–1045. https://doi.org/10.1038/bjc.2017.45
Pujol, J. L., Molinier, O., Ebert, W., Daurès, J. P., Barlesi, F., Buccheri, G., Paesmans, M., Quoix, E., Moro-Sibilot, D., Szturmowicz, M., Bréchot, J. M., Muley, T., & Grenier, J. (2004). CYFRA 21-1 is a prognostic determinant in non-small-cell lung cancer: Results of a meta-analysis in 2063 patients. British Journal of Cancer, 90(11), 2097–2105. https://doi.org/10.1038/sj.bjc.6601851
Molina, R., Agustí, C., Filella, X., Vicent, R., Pahisa, J., Muñoz, M., & Ballesta, A. (1994). CYFRA 21-1 in lung cancer: Comparison with CEA, CA 125, SCC and NSE serum levels. International Journal of Biological Markers, 9(2), 96–101. https://doi.org/10.1177/172460099400900206
Nakamura, T., Ide, H., Eguchi, R., Hayashi, K., Takasaki, K., & Watanabe, S. (1998). CYFRA 21-1 as a tumor marker for squamous cell carcinoma of the esophagus. Diseases of the Esophagus, 11(1), 35–39. https://doi.org/10.1093/dote/11.1.35
Eskelinen, M., & Tikkanen, M. (1998). Cytokeratin 19 fragment (CYFRA 21-1) in lung cancer—a review. Anticancer Research, 18(4C), 2999–3002.
Stieber, P., Hasholzner, U., Bodenmüller, H., Dinges, S., Blum, A., & Fateh-Moghadam, A. (1993). CYFRA 21-1. A new marker in lung cancer. European Journal of Clinical Chemistry and Clinical Biochemistry, 31(10), 652–658.
FAQ’s:
1. What is Cyfra 21-1?
It is a cytokeratin 19 fragment used as a sensitive marker for lung cancer.
2. Why do doctors order it?
To diagnose non-small cell lung cancer, monitor treatment, and track potential relapses.
3. What are normal reference ranges?
The overall normal serum reference range typically falls between 0.66 and 3.84 ng/mL.
4. What causes mild elevations?
Early-stage malignancies or benign lung conditions like COPD, pneumonia, and pulmonary fibrosis.
5. What do high levels suggest?
Values above 10 ng/mL strongly suggest epithelial malignancy or squamous cell lung carcinoma.
6. How is blood collected?
By collecting 3 mL in a red or serum separator tube and separating serum promptly.
7. Can other conditions raise levels?
Yes, liver disease, renal failure, mesothelioma, and extrapulmonary malignancies can cause false positives.
8. What factors interfere with tests?
Icteric, lipemic, or hemolyzed serum samples can interfere with accurate laboratory results.
9. Is it used for screening?
No, general population screening is not recommended for this specific biomarker test.
10. How is treatment success tracked?
A fall in serum levels indicates a good response to ongoing medical therapy.
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