Cancer antigen 125
To monitor treatment for ovarian cancer
Before starting therapy for ovarian cancer or if at high risk for developing ovarian cancer, and at intervals during and after treatment
A blood sample drawn from a vein in the arm
CA-125 is a protein often found on the surface of ovarian cancer cells and in some normal tissues. It is used as a marker for ovarian cancer. However, CA-125 levels may also be high in non-cancerous conditions, including pelvic inflammatory disease, any condition causing excessive fluid in the abdomen (ascites) such as liver disease and in healthy women during pregnancy and menstruation.
Blood is drawn from a vein in the arm.
No test preparation is needed.
CA-125 is used to monitor therapy during treatment for ovarian cancer. CA-125 is also used to detect whether cancer has come back after treatment is complete.
Before a patient starts treatment for ovarian cancer, the doctor will measure a baseline CA-125 to compare against future measurements. During therapy, doctors use CA-125 testing, at intervals, to monitor the response to therapy. CA-125 may also be measured periodically after therapy is completed to catch any early signs of the cancer’s return.
If CA-125 levels fall during therapy, this generally indicates that the cancer is responding to treatment. If CA-125 levels rise, the cancer may not be responding to treatment. High CA-125 levels after treatment is complete may indicate that the cancer has come back.
Because CA-125 can be high in many normal or non-cancerous (benign) conditions (for example, pregnancy, menstruation, endometriosis, pelvic inflammatory disease) it is not useful as a screening test for cancer.
No, not all ovarian cancers are associated with increased levels of CA-125, especially early in the disease. Elevated levels have been found in about 80% of women with ovarian cancer.
No. CA-125 may be elevated in several other conditions and diseases. CA-125 may be high in non-cancerous conditions, including pelvic inflammatory disease, any condition causing excessive fluid in the abdomen (ascites) such as liver disease and in healthy women during pregnancy and menstruation.
Tumour markers, BRCA-1 and BRCA-2
Conditions: Ovarian cancer
RCPA Manual: tumour markers
Healthdirect Australia: Ovarian cancer
Cancer Council Australia: ovarian cancer
Ovarian Cancer Australia
Last Review Date: February 15, 2020