What Is Cancer Antigen 125/ CA 125: Tumor Antigen 125, Causes, Symptoms and Complications,Treatment, Prevention, Interpretation Of Results

CA 125 (acronym for Cancer Antigen 125 ) is a marker of ovarian cancer , which in Europe represents about 5% offemale cancers and in Italy it affects roughly 4,000/5,000 women every year.
In this sense, the CA 125 can be useful in the screening phase (identification of subjects at risk), but above all to monitor the clinical progress of ovarian neoplasms after treatment.


The carbohydrate (or carbohydrate) antigen 125 – CA 125 – is a glycoprotein, i.e. a protein linked to a chain composed of carbohydrates and defined as a glycan. This is produced by the uterus , cervix , fallopian tubes and cells lining organs in the airways and abdomen . When one of these tissues is damaged or inflamed, such as during the development of ovarian cancer, it is possible to find an increase in the amount of CA 125, easily identifiable with a simple blood test .

In addition to ovarian cancer, however, a high value of this marker can also indicate other pathological and non-pathological conditions, including:

  • Pelvic inflammations ;
  • Ovarian cysts ;
  • Presence of menstrual cycle ;
  • Liver pathology ;
  • Tumors of the endometrium , peritoneum and tubes;
  • Endometriosis ;
  • Pancreatitis ;
  • Pregnancy .

To remember
The possibility of a non-specific increase in CA 125 excludes its validity as a screening test for ovarian cancer , while its usefulness is proven to follow the evolution of the disease, once diagnosed.

Because You Measure

CA 125 belongs to the category of so-called tumor “markers” , i.e. those substances which can be found in increased quantities in the blood , urine or other body fluids in the presence of some neoplasms.
Currently, the CA 125 dosage is mainly used to check the outcome of the treatment adopted for ovarian cancer or to reinforce or confirm the diagnosis of this pathology.
Furthermore, in consideration of the insidious evolution of the disease, the analysis of this marker is usually recommended for women who have a higher risk of developing theovarian cancer , such as those who have a family history.
In the event that the symptomatology is suspected and the antigen is increased, however, another test is typically combined, namely the dosage of HE4 (Human epididymis protein 4). The latter marker is more specific than CA 125 and is overexpressed in ovarian cancer. HE4 therefore represents a useful complement of investigation in discriminating between cancer and benign ovarian masses, in the case of positivity of CA 125.

Currently, the combination of multiple markers (such as SMRP, HE4 and CA 72-4) capable of establishing more certain diagnoses of ovarian cancer compared to the use of CA 125 alone is being studied . even abnormal, but benign conditions.

The test is not ordered for women whose tumor antigen 125 levels are normal before starting therapy. In this situation, in fact, the tumor does not produce this marker, which is not useful in monitoring the disease.

In women with a pelvic mass detected or in those at high risk, the presence of elevated CA-125 levels raises the suspicion of ovarian cancer, but is not diagnostic of its presence. Therefore, the diagnosis of ovarian cancer always requires further investigation.

Ca 125 As A Screening Test

CA 125 does not even qualify to be considered a good marker for the early diagnosis of ovarian cancer, since its blood levels often do not increase significantly in the first stage of the disease (as happens in about 50% of cases).
The sensitivity of CA 125 is also reduced by the evidence that a good percentage of ovarian tumors (about 20%) are negative to the test even in the later stages, therefore it is not accompanied by clinically appreciable increases in its plasma levels .
For all these reasons, CA 125 cannot be used on a large scale in cancer screening, but only in the follow-up of ovarian cancer, for which it ensures a sensitivity close to 100% against recurrences.

When Is The Test Prescribed?

The dosage of CA 125 is generally requested before starting a therapy for ovarian cancer. During treatment, the examination can be performed at regular intervals in order to evaluate its effectiveness and detect any relapses.
CA 125 testing may also be indicated after a pelvic mass is detected or in patients at high risk of developing ovarian cancer.

Normal Values

The reference range for CA 125 is 0 to 35 units/ml.

Ca 125 High – Causes

Unfortunately, due to the low specificity , the plasma level of CA 125 cannot be used as an absolute marker of the presence or absence of a malignant pathology (ovarian, in primis).

Benign Diseases

The levels of tumor antigen 125 can in fact be elevated (> 35 U/ml) even in the course of benign diseases, such as:

  • Endometriosis;
  • Uterine fibroids ;
  • Ovarian polycystosis ;
  • Pelvic inflammatory disease ;
  • Pregnancy.


In addition to ovarian cancer, CA 125 levels are also elevated in other types of cancer, such as those originating in the endometrium, fallopian tubes, lungs, breasts , and gastrointestinal tract .
Approximately 2% of healthy women are thought to have CA 125 plasma levels above normal (> 35 U/ml).

How To Measure

The CA 125 test is a laboratory analysis that is performed with a simple peripheral blood sample.


Fasting for at least 8 hours is required for the CA 125 test to avoid food interfering with the result. Taking medicines does not influence the outcome of the analysis, except for those specific for the treatment of tumours.

Interpretation Of Results

In general, the value of CA 125 is increased in ovarian tumors. However, this may also occasionally be elevated in other types of cancer (e.g. uterus, fallopian tubes or intestine ). Therefore, if there is an increase in CA 125 in an otherwise healthy woman, the doctor will recommend a series of appropriate tests to ascertain the presence of a neoplastic disease.
In women undergoing treatment for ovarian cancer, the reduction in CA 125 levels indicates that the disease is responding well to treatment. When the values ​​do not decrease or start to increase again after an initial reduction, they are indicative of a lack of response to therapy.
The presence of high levels of CA 125 after the end of the therapy, on the other hand, suggests the appearance of a recurrence.

Interpretation Of Results In The Course Of Ovarian Cancer

Rather than referring to an absolute cut-off value, in subjects at risk of developing ovarian neoplasia, it would be appropriate to evaluate the trend of CA 125 levels over time. Furthermore, the low degrees of specificity and sensitivity impose that the results are interpreted in a diagnostic key only in a global context that provides for further investigations and procedures (such as ultrasound data).
Another tumor marker , called HE4 ( Human epididymis protein , so called because it was initially identified in the epididymis) increases in the presence of ovarian cancer in a much more specific way, therefore it can be of great help in discriminating between ovarian cancer and cysts or benign ovarian masses.
The CA 125 is however very useful in monitoring patients with operated ovarian cancer; the rise in the values ​​of this tumor antigen after surgery is in fact a warning sign of a resumption of the disease.
For the same reason, during chemotherapy , the CA 125 dosage can provide useful information on the patient’s response to treatment: high values ​​are generally associated with a lack of response to treatment, while continuous increases are indicative of disease progression.
CA125 elevation precedes clinical recurrence by about 3 months.

Similar Posts