Cancer Antigen (CA) 125

Cancer Antigen (CA) 125, also referred to as CA‑125, is used to aid diagnosis of epithelial ovarian cancer in the appropriate clinical context, to monitor disease course and therapeutic response, and to detect ovarian cancer recurrence. When combined with other tumor markers such as CA 72‑4 or HE4, overall diagnostic sensitivity may be higher.

Ovarian cancer represents approximately 4% to 6% of female malignancies and frequently presents without specific early symptoms. Tumor markers complement physical examination and imaging in this setting. CA 125 is a high–molecular‑weight glycoprotein present on ovarian epithelial tumor cells and also found in normal tissues, including pericardium, pleura, peritoneum, endometrium, and testes. Marked serum elevations are common in ovarian malignancy and occur less often with other cancers (eg, endometrial, colorectal, lung, breast, pancreatic). Because expression and serum increases are also seen in healthy women and in benign or inflammatory disorders—such as benign ovarian and uterine conditions, endometriosis, peritonitis, pleuritis, chronic hepatitis or cirrhosis, and chronic pancreatitis—interpretation requires clinical context. Persistent elevation in postmenopausal women is more strongly associated with malignant epithelial ovarian tumors. CA 72‑4 can be elevated in mucinous ovarian carcinoma and in other adenocarcinomas; assessing CA 125 together with CA 72‑4 has been reported to raise diagnostic sensitivity to approximately 73%.