What Are the Three Lung Cancer Marker Tests?
Lung cancer is a severe disease with high mortality and incidence rates. Chemotherapy and radiotherapy should be promptly administered upon discovery of lung cancer to suppress the spread of cancer cells. Common detection methods for lung cancer include carcinoembryonic antigen (CEA), β2-microglobulin, and ferritin. A positive CEA test suggests the presence of lung cancer symptoms, and the CEA level in the blood can be examined to confirm the type of cancer.
1. Carcinoembryonic Antigen (CEA). CEA can be used to detect various tumors that produce and secrete CEA and enter the local body fluids and blood circulation, such as colon cancer, rectal cancer, lung cancer, and pancreatic cancer. Elevated CEA levels can be detected in the serum, plasma, and various body fluids of these patients. CEA measurements are helpful for assisting in diagnosis, prognosis, and efficacy monitoring, but they have high false-positive and false-negative rates. The positive rate of SCEA detection is closely related to the stage of lung cancer and can detect changes in the condition. When the value is more than three times the normal level, it may indicate the possibility of systemic metastasis. For patients undergoing lung cancer surgery, there may be a short-term increase in SCEA levels, which usually decrease and return to normal within about two months. If the levels do not decrease or continue to rise, metastasis should be considered. Common CEA detection methods include radioimmunoassay and enzyme-linked immunosorbent assay.
2. β2-Microglobulin. β2-Microglobulin is elevated in various hematological diseases and solid malignancies and is negatively correlated with CEA. Simultaneous detection of CEA and β2-microglobulin can be complementary, leading to a positive marker in more patients, which is beneficial for prognosis prediction. The positive rate of SCEA is highest in adenocarcinoma patients with lung cancer, followed by squamous cell carcinoma and SCLC. The positive rate of β2-microglobulin is highest in adenosquamous carcinoma and squamous cell carcinoma, followed by adenocarcinoma and SCLC. SCEA levels increase with disease progression and decrease or normalize with disease control, while the results for β2-microglobulin are the opposite.
3. Ferritin. Ferritin is a ubiquitous iron storage protein in the human body that plays an important role in iron storage and metabolism. Recently, it has been used as a tumor marker to assist in the diagnosis and prognosis of lung cancer. However, serum ferritin is not a specific tumor marker and has limited significance in the differential diagnosis of lung diseases. It is also not helpful for early diagnosis of lung cancer. Nevertheless, it has certain clinical value in detecting the progression of lung cancer, tumor growth, recurrence, and metastasis. About one-third of lung cancer patients have elevated ferritin levels, but the reason for this is unknown. It is generally believed that it may be related to abnormal abilities of tumor cells to synthesize and secrete ferritin, necrosis of tumor cells themselves, tissue damage and cell destruction caused by chemotherapy or radiotherapy, resulting in increased release of ferritin from cell cytoplasm, and decreased clearance of ferritin due to liver function impairment.
Ferritin can also be used as a good indicator for distinguishing benign and malignant pleural and ascitic fluids. When the ferritin concentration in pleural and ascitic fluids is >500ng/ml, malignancy should be suspected. When it is >1000ng/ml, it helps establish a malignant diagnosis with a sensitivity of 76%, specificity of 94%, positive diagnostic accuracy of 91%, and negative diagnostic accuracy of 83%.
