Cancerous cells and tumors often produce a specific protein in the blood that can serve as a tumor marker for the cancer. Circulating tumor cells are cells that break off from the cancer and move into the blood stream – protein markers and circulating tumor cells can be measured with very specific blood tests. Tumor marker (biomarker) CA-125 is a test which can help to identify some types of cancer. It is actually the cancer antigen 125 – the protein found on the surface of many ovarian cancer cells. This tumor marker was first identified in the early 1980s. It can be also found in other cancers and in small amounts of normal tissue (not cancerous). CA-125 test measures the amount of cancer antigen protein in the blood but sometimes it can be measured in body fluids taken from the chest or stomach area.
In most cases CA-125 test is used for evaluation of ovarian cancer treatment – for checking the effectiveness of treatment protocols and for discovering the recurrences.
Thanks to tumor marker CA-125 the following can be checked:
- If selected treatment methodology is working,
- If levels of CA-125 going down during or after treatment,
- If ovarian cancer has returned,
- If metastases have been developed.
High levels of CA-125 can be considered as strong sign that the cancer started in the ovary but some types of cancer can also trigger increased levels of CA-125. At the same time, CA-125 test cannot be recommended as a screening test for ovarian cancer because it often has false-positive results.
In general, cancer antigen 125 normal values are:
Less than 35 units per milliliter (U/mL) or
Less than 35 kiloUnits per liter (kU/L) (SI units).
Results of CA-125 test can be affected by recent radioactive scanning, some cancer treating medications and abdominal surgery during first 3 weeks.
According to medical experts, the CA-125 test cannot identify the difference between cancerous and non-cancerous ovarian lump.
It was noted that high levels of CA 125 can be found during different cancerous and non-cancerous diseases. Increased levels of tumor marker CA125 can be detected during following types of cancer:
Tumor marker CA-125
- ovarian cancer,
- cancer of Fallopian tubes (rare),
- uterine cancer (endometrium),
- cervical cancer,
- breast cancer,
- lung cancer,
- stomach or esophagus cancer,
- colorectal cancer,
- pancreatic cancer,
- liver cancer,
- lymphoma.
According to medical experts CA 125 also can be increased during endometriosis, ovarian cysts, pelvic inflammatory disease (PID), menstruation, pregnancy, uterine fibroids, lupus, pancreatitis, pleurisy, cirrhosis or hepatitis.
CA 125 test can be very useful – decrease or return to normal values could mean that the cancer has responded well to treatment. Usually slight increase is not significant but real increase of CA 125 could mean that the cancer is not responding well to treatment or it is still growing or is coming back (recurring).
Although tumor marker CA 125 is a useful test during treatment monitoring in women suffering from ovarian cancer, single CA 125 test cannot be considered as a screening test for cancer. Some women with ovarian cancer (up to 20%) never have elevated CA-125 levels, while most women with elevated CA-125 levels don’t have cancer. According to medical statistics, results of CA-125 testing can be elevated in several non-cancerous conditions and only about 3% of women with elevated CA-125 levels have ovarian cancer.
It was noted that CA-125 test is more accurate after 50 – if postmenopausal woman has a tumor and increased levels of CA-125, she has an extremely high risk of having a cancer. In young women the CA-125 test can be pretty inaccurate.
