Patients with lung cancer usually have a poor prognosis. The lack of effective treatment for disease recurrence limits the use of tumor marker assays in the clinic, especially in follow-up. However, in any case, tumor marker assays are helpful in the clinic. the EGTM guidelines suggest that tumor markers can be used appropriately for differential diagnosis and efficacy monitoring. Most primary lung cancers can be classified into four major pathological types-squamous cell carcinoma, adenocarcinoma, large cell lung cancer, and small cell lung cancer (SCLC). Twenty to 25% of all tumors of bronchogenic origin are SCLC, which is clinically and physiologically distinct from the other three types (often referred to as non-small cell lung cancer NSCLC). It is now well established that many tumors have more than one cancer pathology type. both SCLC and NSCLC exhibit heterogeneous genomes in which the major pathological types of lung cancer overlap. Tumor markers used in lung cancer Tumor markers commonly used in lung cancer are neuron-specific enolase (NSE), carcinoembryonic antigen (CEA), CYFRA21-1, squamous cell carcinoma-associated antigen (SCCA), and progranulin-releasing peptide (ProGRP). Neurospecific enolase (NSE) The glycolytic enzyme enolase (2-phospho-D-glycerate hydrolase) exists as a series of isozyme dimers (αα, αβ, ββ, and γγ). αγ and γγ enolase isozymes are also known as neuron-specific enolases (NSE) because they are produced by central and peripheral neurons and neuroectodermal malignancies (SCLC, neuro blastoma, intestinal cancer) are produced. CYFRA 21-1 CYFRA 21-1 is a relatively new tumor marker, measured with two monoclonal antibodies to the anti-cytokeratin 19 fragment. Immunohistochemical studies have shown that lung cancer is enriched in cytokeratin 19 fragments, and CYFRA 21-1 is the most sensitive tumor marker for NSCLC. Because CYFRA 21-1 represents only one fragment of cytokeratin 19, CYFRA 21-1 has a higher specificity than tissue polypeptide antigen (TPA) [identifying cytokeratin 8, 18, and 19 fragments]. Progastrin-releasing peptide (ProGRP) ProGRP is a relatively stable precursor of the hormone gastrin-releasing peptide (GRP). In humans, GRP is mainly found in the gastrointestinal and respiratory tracts to the central nervous system. Some studies suggest that GRP is released by tumor cells in small cell lung cancer and that GRP may stimulate the growth of SCLC cells. proGRP has not been included in the EGTM guidelines. Tumor markers in lung cancer clinics Screening and diagnosis The lack of sensitivity and organ and tumor specificity means that none of the above tumor markers are suitable for screening for lung cancer (either in asymptomatic people or in those at high risk for tumors). The diagnosis of lung cancer is mainly based on medical imaging, endoscopy, surgery and pathology. Although tumor marker measurements are not a substitute for pathology results, they can be very helpful in cases where a pathology biopsy does not make a final diagnosis (in about 20% of cases). For example, elevated serum and tissue NSE in patients lacking pathologic evidence may support the diagnosis of SCLC. Similarly, patients with high serum SCCA levels are highly suspicious for patients with NSCLC and squamous cell carcinoma.CYFRA 21-1 is overall highly specific for lung cancer. Although serum CYFRA 21-1, TPA, NSE and CEA were all associated with tumor burden, there was no consistent correlation between the stage of tumor development and the production of these tumor markers. Overall, however, it appears that high tumor marker concentrations reflect the progression of disease in tumor patients and suggest a poor prognosis. A slow or moderate decrease in tumor marker concentrations does not preclude tumor progression or development. Pre-treatment tumor marker testing can be helpful in the diagnosis of primary tumors. Elevated tumor marker levels after surgery indicate the continued presence of tumor and ineffective treatment. Prognosis Data from a survey analysis of all markers in patients with NSCLC and SCLC indicate that CYFRA 21-1 has high application for NSCLC and is a significant prognostic factor in multivariate analysis. Post-treatment monitoring The results of lung cancer tumor markers are important indicators for evaluating the efficacy and surgical outcome. Like tumor markers in other cancers, the reduction of corresponding tumor marker levels after surgery suggests the therapeutic efficacy and good prognosis of surgery. A slow decrease in tumor marker concentration or (and) a decrease below the reference range indicates the presence of tumor or metastasis. The risk of recurrence of lung cancer is high (70-90%). Monitoring with tumor markers for subsequent treatment can only be done after the treatment plan has been determined, but the basal level after surgery needs to be established and an increase in the level of tumor markers from this basal level is the first sign of disease recurrence.