cancer Antigen 125 (CA125) in diagnosis of cancer

Last edited 03/2023 and last reviewed 10/2023

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)

Reference:

• Charkhchi P, Cybulski C, Gronwald J, Wong FO, Narod SA, Akbari MR. CA125 and Ovarian Cancer: A Comprehensive Review. Cancers (Basel). 2020 Dec 11;12(12):3730. doi:10.3390/cancers12123730.
• Dochez V et al. Biomarkers and algorithms for diagnosis of ovarian cancer: CA125, HE4, RMI and ROMA, a review. J Ovarian Res 12, 28 (2019). https://doi.org/10.1186/s1304-019-0503-7
• Liu L, Xu HX, Wang WQ, Wu CT, Xiang JF, Liu C, Long J, Xu J, Fu de L, Ni QX, Houchen CW, Postier RG, Li M, Yu XJ. Serum CA125 is a novel predictive marker for pancreatic cancer metastasis and correlates with the metastasis-associated burden. Oncotarget. 2016 Feb 2;7(5):5943-56. doi: 10.18632/oncotarget.6819.
• Gandhi T, Zubair M, Bhatt H. Cancer Antigen 125. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK562245/