The CA125 blood test measures the amount of cancer antigen 125 protein present in a person’s blood. The protein is commonly associated with ovarian cancer, and the CA125 blood test can be a helpful tool for healthcare providers to monitor the effectiveness of ovarian cancer treatment.
What is the CA125 protein?
Despite its name and association with ovarian cancer, low levels of the CA125 protein are present in everyone’s blood—including in men and people without ovaries. It is considered a tumour marker in the blood but, like many tumour markers, can be related to benign and non-cancerous conditions.
Cancer Council SA 13 11 20 nurse Deb Roffe says CA125 blood tests can help doctors investigate a number of conditions.
“Elevated CA125 protein levels have been linked to some infections, chronic health conditions like endometriosis and fibroids, and can even be influenced by ovulation,” she says.
How is the CA125 protein linked to cancer?
Some types of cancer can produce CA125 protein. It is mostly linked to types of ovarian cancers, but other types of cancer can also produce CA125 protein.
Can the CA125 blood test be used to diagnose cancer?
The CA125 blood test by itself can’t be used to diagnose ovarian cancer, nor can it be used as a screening tool. In many cases, someone with early-stage ovarian cancer may not have elevated levels of CA125 protein in their blood. The CA125 blood test can also show elevated levels of CA125 protein in people who do not have cancer.
“The CA125 blood test can still be a helpful tool for healthcare providers in diagnosing or ruling out ovarian cancer when used alongside other tests, like an ultrasound,” Deb says.
How is the CA125 blood test used?
A healthcare provider may use the CA125 blood test to help monitor the effectiveness of cancer treatment. For types of cancer which produce the protein, regular tests which show CA125 protein levels are falling could be an indicator that cancer treatment is working. Conversely, rising or steady levels of CA125 protein across regular blood tests could indicate treatment is not working well.
The CA125 blood tests can also be included in follow-up tests after treatment.
Who should get a CA125 blood test?
For people who have a family history of ovarian cancer, who have a genetic mutation which puts them at a higher risk of ovarian cancer, or who are showing symptoms of ovarian cancer, a healthcare provider might suggest monitoring CA125 protein levels through regular blood tests.
What if my blood test shows elevated CA125 protein levels?
Speak to your healthcare provider. Having elevated CA125 protein levels can mean several things and your healthcare provider may choose to investigate further.
“Doctors like to focus on patterns over time, and CA125 protein levels need to be considered alongside any symptoms which may be present and other tests,” Deb says.
“An elevated result doesn’t necessarily mean a person has cancer.”
