Algorithm for the determination of oncomarkers

Specificity of tumor markers is the percentage of healthy individuals and patients with benign tumors in whom the test gives a negative result.

Sensitivity of a tumor marker is the percentage of results that are true positive in the presence of a given tumor.

The threshold concentration (cutoff point) is the upper limit of the tumor marker concentration in healthy individuals and patients with non-malignant neoplasms.

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The goals of tumor marker determination in clinical practice

• An additional method for diagnosing oncological diseases in combination with other research methods.
• Management of cancer patients - monitoring of therapy and control of the course of the disease, identification of tumor remnants, multiple tumors and metastases (the concentration of the tumor marker may increase after treatment due to tumor disintegration, so the study should be carried out 14-21 days after the start of treatment).
• Early detection of tumors and metastases (screening in risk groups - PSA and AFP);
• Determining the prognosis of the disease.

Scheme of appointment of tumor marker studies

1. Determine the level of tumor markers before treatment and subsequently examine those tumor markers that were elevated.
2. After the course of treatment (surgery), examine after 2-10 days (according to the half-life of the marker) in order to establish a baseline level for further monitoring.
3. To assess the effectiveness of treatment (surgery), conduct a study after 1 month.
4. Further study of the tumor marker level in the blood should be carried out once a month for the first year after treatment, once every 2 months for the second year after treatment, once every 3 months for 3-5 years (WHO recommendations).
5. Conduct tumor marker testing before any change in treatment.
6. Determine the level of tumor markers if relapse and metastasis are suspected.
7. Determine the level of the tumor marker 3-4 weeks after the first detection of its increase.

Factors influencing in vitro the concentration of tumor markers in the blood

• Storage conditions for blood serum (must be kept cold).
• The time between sample collection and centrifugation (no more than 1 hour).
• Hemolyzed blood serum (increased concentration of NSE).
• Sample contamination (increased concentration of CEA and CA 19-9).
• Taking medications (ascorbic acid, estradiol, ions of di- and trivalent metals, guanidine analogues, nitrates, etc. increase the concentration of PSA).

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Factors influencing in vivo the concentration of tumor markers in the blood

• Production of tumor markers by a tumor.
• Release of a tumor marker into the blood.
• Tumor mass.
• Blood supply to the tumor.
• Daily variations (blood must be taken for testing at the same time).
• Body position at the time of blood collection.
• The influence of instrumental studies (X-ray increases the concentration of NSE; colonoscopy, digital rectal examination - PSA; biopsy - AFP).
• Catabolism of tumor marker (functioning of kidneys, liver, cholestasis).
• Alcoholism, smoking.

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