CA125 in Ovarian Cancer Management

Primary Uses and Limitations

The American College of Radiology recommends CA125 as a tumor marker for monitoring response to treatment, detecting recurrence, and helping differentiate pelvic masses in ovarian cancer, with a true-positive rate increasing to approximately 80% with stage II or greater ovarian cancer 1, 2
CA125 has poor sensitivity for early-stage ovarian cancer, with only about 50% of stage I ovarian cancer patients showing elevated levels, and lacks specificity as a standalone screening tool due to false-positive results in various benign conditions 1, 2, 7
The Gynecologic Cancer InterGroup (GCIG) has established criteria for using CA125 to assess response and progression in ovarian cancer, which can be used in combination with other diagnostic modalities for improved diagnostic accuracy 3, 4

The National Comprehensive Cancer Network (NCCN) recommends CA125 monitoring during follow-up visits for ovarian cancer patients, especially if initially elevated, with normal CA125 values typically below 35 U/mL and higher specificity (98.5%) for women over 50 years of age 1, 5, 9, 11
Serial monitoring of CA125 levels can detect recurrent disease before clinical symptoms appear, and when elevated CA125 levels are detected during surveillance, imaging studies (CT, MRI, or PET-CT) are indicated to evaluate for recurrence 9, 11
A high CA125/CEA ratio can help differentiate ovarian from gastrointestinal primary tumors, and progressive elevation of CA125 over time, even within normal range, may indicate malignancy and warrants further evaluation 1, 5, 10