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Cancer antigen CA-125 in the blood
Medical expert of the article
Last reviewed: 23.04.2024
CA-125 is a glycoprotein present in serous membranes and tissues. In women of childbearing age, the main source of CA-125 is the endometrium, which is associated with a cyclic change in the level of CA-125 in the blood, depending on the phase of the menstrual cycle. During menstruation, the concentration of CA-125 in the blood rises. In pregnancy, CA-125 is detected in the placenta extract, in the pregnant serum (I trimester), in amniotic fluid (16-20 weeks). In healthy women, the level of CA-125 in blood is affected by the synthesis of this marker in the mesothelium of the abdominal and pleural cavities, the pericardium, the epithelium of the bronchi, the fallopian tubes, the ovaries, and in men (in addition to the serous cavities) - in the epithelium of the testes.
Reference values (norm) of CA-125 in women in serum up to 35 IU / ml; at pregnancy - up to 100 IU / ml; in men - up to 10 IU / ml. The half-life is 4 days.
[Indications for the purpose of the assay
Determination of the content of CA-125 in serum is used:
- for the diagnosis of recurrent ovarian cancer;
- to monitor treatment and control of ovarian cancer;
- for diagnosis of neoplasms of the peritoneum, pleura;
- To diagnose serous effusion in the cavity (peritonitis, pleurisy);
- for the diagnosis of endometriosis.
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The causes of increased CA-125 in the blood
The concentration of CA-125 in the blood increases with various non-tumorous diseases with the involvement of serous membranes in the process - peritonitis, pericarditis, pleurisy of different etiologies. A more significant increase in the level of CA-125 in the blood is sometimes observed in various benign gynecological tumors (ovarian cysts), as well as in inflammatory processes involving appendages and benign endometrial hyperplasia. However, in most of these cases, the concentration of CA-125 in serum does not exceed 100 IU / ml. A slight increase in the level of this marker is revealed in the first trimester of pregnancy, with various autoimmune diseases (collagenoses), hepatitis, chronic pancreatitis and cirrhosis.
In patients with congestive heart failure, the CA-125 concentration in the blood correlates with the level of natriuretic peptides, so it can be used as an additional criterion for assessing the severity of heart failure.
The CA-125 blood test is used mainly to monitor serous ovarian cancer and to diagnose its relapse. At a 65 IU / mL separation point, CA-125 has a sensitivity of up to 87%, depending on the stage and histological type of tumor. In 83% of patients with ovarian cancer, its level is on the average 124-164 IU / ml. For serous ovarian cancer, the level of increase in serum CA-125 depends on the stage of the tumor: in the I-II stage, CA-125 increases in about 50% of cases, and in the III-IV stage - in all patients. In patients with ascitic forms of ovarian cancer, the concentration of CA-125 in serum may exceed values of 10,000-20,000 IU / ml. Regression of a tumor with effective chemotherapeutic or chemoradiotherapy or surgical removal is accompanied by a decrease in the content of CA-125 in the blood. Raising the level of CA-125 in the blood is associated with the progression of the tumor process. To assess the effectiveness of chemotherapy, it is necessary to investigate the level of CA-125 in the blood before the beginning of each course of treatment, and after its completion with a periodicity of 1-2 months.
In contrast to serous ovarian cancer, in other histological types of ovarian cancer (mucinous, endometrioid and clear cell), its content rises in 25-30% of cases. With teratomas and dyshermomas of the ovaries, an elevated level of CA-125 in the blood is recorded only in individual patients with ascites and metastases in the abdominal cavity.
CA-125 is a useful marker for evaluating the effectiveness of treatment and early detection of recurrences of endometriosis, which ranks second after ovarian cancer in the number of patients with a high content of CA-125. The increase in CA-125 level in the blood correlates with the stage of endometriosis: at stage I-II the concentration of the marker is increased in 25% of patients, and at stage III-IV - in 54%. As a rule, the concentration of CA-125 in serum in such patients does not exceed 65 IU / ml.
The level of CA-125 is increased in 15-30% of patients with malignant tumors of the gastrointestinal tract, pancreas, bronchi, and breast. Values of CA-125 in the serum of these patients, exceeding 150-200 IU / ml, indicate the involvement of serous membranes in the process.