What Level of CA 125 Indicates Cancer?

Reviewed on 1/12/2021

What Is CA 125?

CA 125 is a kind of protein, spikes in the levels of which may indicate ovarian cancer. The normal range for CA 125 is 0 to 35 units/ml, but increases may indicate conditions other than cancer, and thus this test must be done in conjunction with other diagnostic tools to confirm the presence of cancer.
CA 125 is a kind of protein, spikes in the levels of which may indicate ovarian cancer. The normal range for CA 125 is 0 to 35 units/ml, but increases may indicate conditions other than cancer, and thus this test must be done in conjunction with other diagnostic tools to confirm the presence of cancer.

CA 125 is a glycoprotein (a sugar-associated protein) found in the blood that is considered a biomarker (or “tumor marker”) because it is found in greater concentrations in ovarian cancer cells. 

What Is CA 125 Measurement Used to Diagnose? 

CA 125 is commonly used:

  • To help diagnose ovarian cancer in women at risk
  • To detect recurrent ovarian cancer in women who have been previously treated
  • To help predict treatment outcome in women with ovarian cancer and closely related cancers, such as fallopian tube and primary peritoneal cancers
  • To monitor or assess treatment effectiveness
  • To screen for ovarian, primary peritoneal, and fallopian tube cancers in high-risk women or in women with abnormal findings on examination or ultrasound
  • Used as a marker to help determine the risk of a malignancy preoperatively

What Are Limits of the CA 125 Test?

Limits of the CA 125 test include: 

  • CA 125 is only elevated in about half of women who have early-stage ovarian cancer and 85% of women with advanced ovarian cancer
  • This means a woman may have ovarian cancer and her levels of CA 125 may not be elevated
  • Levels of CA 125 do not correlate with how much disease a person has 
  • Many noncancerous conditions can also increase CA 125 levels, such as 
  • The National Cancer Institute and the United States Preventive Services Task Force do not recommend use of CA 125 measurements to screen women who have a low risk for developing ovarian cancer 

What Level of CA 125 Indicates Cancer?

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

If you have not been diagnosed with ovarian cancer, high levels will require further testing to make a diagnosis. 

If you have been treated for ovarian cancer, and CA 125 levels are high, it may mean the cancer has returned.

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Reviewed on 1/12/2021
References
https://www.foundationforwomenscancer.org/wp-content/uploads/FWC-CA-125-Levels-Your-Guide.pdf

https://emedicine.medscape.com/article/2087557-overview

https://ocrahope.org/patients/about-ovarian-cancer/symptoms-and-detection/what-is-ca-125/