cancer Antigen 125 (CA125) in diagnosis of cancer

Last edited 03/2023 and last reviewed 03/2023

Cancer Antigen 125 (CA125) in diagnosis of cancer

Cancer Antigen 125 (CA125), also referred to as Carbohydrate Antigen 125

  • CA125 is a high molecular weight mucinous glycoprotein found on the surface of ovarian cancer cells. This antigen is then shed and quantified in serum samples of ovarian cancer patients
    • upper limit is 35 U/mL
    • serum CA125 levels are elevated in 50% of early-stage tumours, which are mostly type I ovarian cancers and 92% of advanced-stage tumours, which are mostly type II ovarian cancers
      • measurement is not very sensitive in the early phases of ovarian cancer (only reported to be elevated in 23 to 50% of stage I cases) (2)
      • elevated serum CA125 levels may be observed in other physiological or pathological conditions (menstruation, pregnancy, endometriosis, inflammatory diseases of the peritoneum) (2)
      • due to the low incidence of ovarian cancer, screening average-risk women with CA125 results in a considerable number of false positives
      • sensitivity of multimodal screening with serial CA125 measurements and transvaginal ultrasound based on risk was 85.8% at a specificity of 99.8%

  • Liu et al described a unique role for serum CA125 levels in pancreatic cancer diagnosis and treatment
    • CA125 levels specifically reflect the metastasis-associated burden of pancreatic cancer in patients with advanced disease, as well as the presence of occult metastasis in patients with clinically localized tumors

  • elevated levels of serum CA 125 (>35 U/mL) were present in 82% of patients with epithelial ovarian cancer, 28.5% of patients with non-gynecological cancers such as pancreatic, lung, breast, colorectal, and 6% of the patients with benign diseases such as an ovarian cyst (4)