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Does CA 125 give a conclusive diagnosis of Ovarian cancer?

What is CA 125?

Firstly, you might want to know what is CA 125 and why is it named as such? CA 125 is also called as Cancer Antigen 125 or Carcinoma Antigen 125 and belongs to a class of proteins known as glycoproteins (sugar associated with protein). It is commonly referred to as a biomarker or tumor marker since information regarding biological state of a disease is provided by it which is measured from your collected blood sample.

CA 125 is widely used in cases of ovarian cancer and is highly beneficial in assessment of women with ovarian cancer. The name CA 125 has an interesting story behind it. It was developed when the investigators were searching for something on surfaces of ovarian cells which could trigger the recognition of tumor cells by immune cells in the body.  It was only on 125th attempt that antibody tested against the ovarian cancer cells was found and that surface signal on tumor cells came to be known as CA 125.

Things you should consider in CA 125 testing

You must keep some important points in mind while going for CA 125 testing. A rise in CA 125 occurs in about 80% of women with ovarian carcinoma originating from epithelial lining cells of ovaries. The degree of elevation correlates with tumor burden and clinically detected stage of ovarian cancer. Anyhow, for the screening and initial diagnosis of ovarian cancer, CA 125 levels alone will not be recommended by your doctor as CA 125 is also released by normal tissues including ovarian, pancreatic, breast cells, lining tissue of abdomen and chest. The benign and malignant conditions related to these tissues and organs which disturb the normal balance of the body lead to rise in the CA 125 levels. Hence, for the conclusive diagnosis of ovarian cancer, your doctor will interpret an elevated CA 125 in the context of the clinical stage/ scenario and indication for which it is being tested.

Further, CA 125 is particularly unreliable in screening pre-menopausal women as both ovulation and menstruation can lead to raised levels of CA 125.


How CA 125 test is used in Ovarian cancer?

The poor outcome of ovarian cancer due to detection of the cancer at the late stage of cancer has led to considerable efforts to develop strategies for early detection of the cancer. The CA 125 test is used during the course of the disease in screening and initial diagnosis, diagnosis and detection of recurrent cancer and how far treatment is successful.

Screening – In case you are at a high risk of ovarian cancer or have abnormal findings on examination or ultrasound, then you are a potential candidate for screening with CA 125 test. Those women who have mutations in Breast cancer genes (BRCA genes), family history of ovarian cancer, past history of ovarian cancer, use hormone replacement therapy, smoke and are possibly obese are considered at high-risk for ovarian cancer. When CA 125 is used by itself, it is not highly effective in detecting ovarian cancer. Your doctor will recommend pelvic ultrasound along with it to screen for ovarian cancer. Hence, sequential screening with CA 125 combined with ultrasound, which is named as multimodal screening leads to an early detection of ovarian cancer. In multimodal screening, there is Level 1 screen which involves measuring CA 125 levels at regular intervals and Level 2 screen which involves doing scan. The outcome of screening is a combination of both the levels which involves confirming the diagnosis and referring for further consultation or keeping you on annual screening of ovarian cancer.

Diagnosis: Lets review the Risk of Malignancy index (RMI) which has been employed in clinical practice for numerous years for conclusive diagnosis of ovarian cancer. RMI is a scoring system based on a combination of your demographic and ultrasound data with measurement of serum CA 125. Serum CA 125 measurement and an abdominal and pelvic ultrasound along with the woman’s menopausal status, are used to calculate this index. Risk of Malignancy index is especially sensitive to rise in CA 125 levels and is used both for benign and malignant ovarian cancers.

Detection and diagnosis of recurrent disease: When the levels of CA 125 rise in the absence of clinical and radiological findings, it is termed as a biochemical relapse which occurs before clinically detected relapse by 2-6 months. CA 125 test provides the most convincing diagnosis of recurrent disease if you have been previously treated for ovarian cancer. Usually, elevation in the CA 125 levels over a series of tests by all means hints at recurrence of your disease.

Monitoring response to treatment: Response to treatment has been defined as the decrease in 50% or more in pre-treatment CA 125 levels maintained for at least 28 days. The CA 125 test is a dependable means to determine if your treatment is working when combined with history and physical exam. The decrease in CA 125 levels correlates with treatment response in this context. It is vital for you to know the initial or pre-treatment value of CA 125 and monitoring is beneficial and accurate when there is an elevated starting value.

It is always reasonable and better to consult your doctor if you have propensity for developing cancer. Early detection and management of disease definitely have a better outcome than waiting for a negative far-reaching consequence of late detection.